Lectures 1 and 2. Laboratory diagnostics — the phases, the order of draw, the specimen studies, point-of-care testing and its regulation, and the statistics. Then medical imaging — the modalities, density and the Hounsfield scale, T1 against T2, positioning and the planes, radiation dose and contrast media. Opens with how Professor Reynolds said this exam is written.
| Term | What you need to know |
|---|---|
| Reference ranges are GIVEN | “I'm not going to just throw a random number at you” — normal ranges are always supplied, on this exam and in every class. Do not spend the night memorizing cutoffs; spend it on what a value means. |
| Tests, not diagnoses | “More related to the tests themselves rather than maybe the specific diagnosis.” What to order, why, its limits, how to read it. The instructional objectives are the blueprint. |
| No predictive-value math | “We're not gonna do math, I'm not gonna make you do math.” Know which DIRECTION prevalence pushes positive predictive value and why — never the formula. |
| Question style | Vignette and next-best-test: “which of the following laboratory tests would be best to evaluate…”, “what would be the next test that you would order?” Images (x-ray, CT, rhythm strip) may accompany the vignette. |
| Term | What you need to know |
|---|---|
| Pretest = preanalytical | Begins with patient preparation, extends until the test begins. History and risk, contraindications, coping styles and fears, universal precautions, documentation, cost, education, consent. |
| MOST ERRORS ARE PRETEST | The single most testable fact here. Communication errors, medication administration, labeling; technical errors — inadequate tube fill, transport delay, wrong storage; inappropriate preparation — fasting. |
| Variables affecting results | Patient preparation · current drug therapy · time of collection · physical activity · hydration · age · sex · body mass index. |
| Intratest = analytical | Performing the test: collection, monitoring the environment, comfort, analgesics and sedatives, vital signs, universal precautions, minimizing delays, watching for complications. |
| Posttest = postanalytical | Aftercare. Complications: bleeding, infection, respiratory difficulty, perforation, sedation effects. Interpret, IDENTIFY AND TREAT CRITICAL VALUES, communicate clearly and sensitively. |
| Integration & follow-up | Diagnosis, acceptance, healing, health-promoting behavior. Education, follow-up labs and appointments, referrals, emotional well-being. “If it wasn't documented, it wasn't done.” |
| Term | What you need to know |
|---|---|
| Stop Light Red Stay Put Green Light Go | Yellow (sterile/blood culture) → Light blue (citrate/COAGS) → Red (non-additive) → Gold SST → Green PST → Green (heparin) → Lavender (EDTA/CBC) → Gray (glycolytic inhibitor). She wants THE ORDER and the broad category, not the full additive table. |
| The four pairings to know cold | Light blue = coagulation. Lavender = complete blood count. Yellow = blood cultures. Gray = glucose. |
| Why the order exists | To avoid cross-contamination of additives between tubes. Carry EDTA into a chemistry tube and the potassium reads wrong. |
| Clear tube | Nonadditive discard tube — fills the collection set's dead space before the coagulation tube when no royal blue is drawn. |
| Term | What you need to know |
|---|---|
| Get it BEFORE antibiotics | Stated for blood, sputum and throat cultures alike. The single rule spanning them. |
| Ova & parasites | DO NOT REFRIGERATE — warm stool is best. THREE separate random specimens, because of the parasite life cycle. Specimen free of urine or other secretions, dry clean container. |
| Guaiac | Heme oxidizes hydrogen peroxide in the guaiac → BLUE = POSITIVE. Use a SMALL sample; a large one obscures the result. Can be done off the gloved finger after digital rectal exam. |
| Blood cultures | Acute febrile illness with suspected septicemia. Diagnostic AND therapeutic (pathogen + sensitivities). TWO samples from OPPOSITE ARMS, ideally pre-antibiotic. AEROBIC FIRST. Scrub, let dry, and do not palpate after disinfection unless sterile-gloved. |
| Sputum culture | Two steps: GRAM STAIN first (positive vs negative), then culture for identification and sensitivities. Upright, rinse mouth with water, three deep breaths, deep cough. Aerosols may assist. Acid-fast bacilli from the same specimen. |
| Throat culture | Streptococci, because of beta-hemolytic streptococcal pharyngitis; commonest ages 3–15. Tongue blade improves view, relaxes throat, reduces gag. Swab posterior throat, BOTH tonsils, any exudate — AVOID tongue and lips. |
| Term | What you need to know |
|---|---|
| Definition | Testing completed OUTSIDE the centralized laboratory, at or close to the site of patient care. Near-patient, remote, satellite, rapid diagnostics. |
| Primary care menu | Glucose · hemoglobin A1c · urinalysis · rapid influenza · rapid strep · fecal occult blood · pregnancy · cholesterol · PT/INR · drug screening. Rapidly increasing: fentanyl and HIV testing. |
| Acute care menu | Venous blood gas · glucose · TROPONIN · brain natriuretic peptide · D-dimer · PT/INR · hemoglobin/hematocrit · rapid antigen · urine hCG · UA dipstick. Machines: portable x-ray, ECG, pulse oximetry, ultrasound. |
| Advantages vs limitations | FOR: convenient, rapid, less manpower, fewer visits, fingerstick not needle stick, better care where resources are limited. AGAINST: expensive, quality assurance hard to control, operator and manufacturer variability, non-standard vocabulary, LESS PRECISE, supply needs. |
| Qualitative / semi-quant / quantitative | Qualitative = rapid strep, flu, pregnancy (positive or negative). SEMI-QUANTITATIVE = urinalysis dipstick (matched to a chart). Quantitative = glucose (highest volume), chemistries, coags, cardiac markers — needs a reader. |
| CLIA complexity | WAIVED = little harm from a false result; the Joint Commission calls all testing outside a traditional lab waived, i.e. POCT. MODERATELY COMPLEX = ~75% of the 12,000 tests, usually automated. HIGHLY COMPLEX = operator skill, e.g. cross match. PROVIDER-PERFORMED MICROSCOPY = provider reads a fresh slide. |
| Who does what | CMS issues certificates, inspects, enforces. FDA categorizes tests by complexity. CDC provides standards, research, quality studies. |
| Regulation goes one way | CLIA is the MINIMUM and cannot be downgraded, so state and city rules are always STRICTER. Every site licensed for ANY testing; license matches complexity; reapply EVERY TWO YEARS. |
| Term | What you need to know |
|---|---|
| SnNout / SpPin | High SENSITIVITY + Negative rules OUT (fewer false negatives; good at DETECTING; best for SCREENING). High SPECIFICITY + Positive rules IN (fewer false positives; good at EXCLUDING; best for CONFIRMING). |
| One dial, two costs | Move the threshold down to catch every case → false positives. Move it up to exclude cleanly → false negatives. You cannot maximize both, which is why HIV screening is sensitive first, confirmatory testing specific second. |
| Test-centered vs patient-centered | Sensitivity and specificity belong to THE TEST. Positive and negative predictive value belong to THE POPULATION being tested. |
| The named trap | “My patient's test is positive — do they have it?” feels like sensitivity. It is POSITIVE PREDICTIVE VALUE. Sensitivity = P(test+ | disease); PPV = P(disease | test+). That reversal is Bayes' theorem. |
| Frostbite — same test, two states | 95% sensitivity and specificity throughout. Michigan, prevalence 10% → PPV ~68%. Florida, prevalence 0.1% → PPV ~2%. Shark bite reverses the geography and the logic holds. |
| Pre-test vs post-test probability | PRE-TEST = likelihood before the result, from signs, symptoms, history, risk factors, how common it is. POST-TEST = likelihood after, depending on sensitivity and specificity. |
| Prevalence vs incidence | PREVALENCE = how COMMONLY something occurs (existing cases, usually a percentage). INCIDENCE = how OFTEN it happens. |
| Screening vs diagnostic | SCREENING: asymptomatic, cheap, easy, indicates whether more testing is needed. DIAGNOSTIC: symptomatic, may be invasive, confirms. A screening test BECOMES diagnostic if an abnormality is found during it — e.g. colonoscopy. |
| Term | What you need to know |
|---|---|
| Radiography | Ionizing radiation, viewed in 2-D. Quick, cheap, available anywhere, portable — the most widely obtained study. Against: only FIVE densities, structures overlap, ionizing radiation (relatively low dose). |
| Computed tomography | Rotating fan beam, thousands of transmission points. EXPANDS THE GRAY SCALE beyond five densities, reduces overlap, works with implanted devices, 3-D reconstruction. THE CORNERSTONE OF CROSS-SECTIONAL IMAGING. Against: not portable, a LOT of radiation, needs space and processing. |
| Ultrasound | High-frequency sound from a transducer, bounced back. NO radiation — the SAFEST modality, and real time, so it is for MOVING structures: heart, vasculature, obstetrics. Color Doppler adds flow DIRECTION and VELOCITY. Often first choice in the FEMALE PELVIS and in PEDIATRICS. Against: cannot penetrate bone, gas disrupts it, deep structures are hard, OPERATOR-DEPENDENT. |
| Magnetic resonance | Magnetic field aligns hydrogen; release emits radio waves — essentially a HYDROGEN MAP. Contrast is GADOLINIUM. Best for SOFT TISSUE, i.e. anything but bone; cornerstone of NEUROIMAGING and orthopedic soft tissue. Calcium emits NO signal, so tissue inside bone is visible. Diffusion-weighted imaging for STROKE. Against: not widely available, expensive, slow, magnetic implants and ferromagnetic projectiles. Not recommended in pregnancy or infants despite no radiation. |
| PET vs SPECT | PET = positrons, FDG-18 (radioactive glucose), 2-D, gamma camera — CANCER STAGING, brain disorders, cardiac blood flow; shows who is EATING GLUCOSE. SPECT = single photons, rotating gantry, 3-D, technetium-99 — heart disease, BONE SCANS, brain; shows WHERE BLOOD FLOWS. |
| Angiographic studies | NOT one test — any modality can image vessels. X-ray → angiogram. Ultrasound → color Doppler. CT angiography → iodine injected quickly. MR angiography → NO DYE NEEDED. Veins = venogram. |
| Fluoroscopy | Ionizing radiation giving REAL-TIME video: motion, positioning, and barium or iodine moving through gut, urinary tract and vessels. Needs a specially fitted unit with a tilting table. |
| Term | What you need to know |
|---|---|
| Five densities, whitest → blackest | METAL · CALCIUM (bone) · FLUID/SOFT TISSUE · FAT · AIR. Fluid and soft tissue have THE SAME DENSITY on a plain film — that is the pair you cannot separate. |
| Hounsfield numbers (SLIDE 13 — an IMAGE, not text) | Air −1000 · Fat ~−40 to −120 · WATER = 0 BY CONVENTION · Soft tissue ~+20 to +100 · Bone ~+400 to +600 · Metal ~+1000 or higher. CT pulls WATER APART from soft tissue — the asterisk on the deck's “Five*”. |
| The vocabulary | RADIOLUCENT = hypodense = DARKER, because MORE beam passed through (less absorbed). RADIOPAQUE = hyperdense = radiodense = WHITER, because LESS passed through (more absorbed). |
| Attenuation | INCREASED attenuation = high Hounsfield number = whiter (metal, calcium). DECREASED attenuation = low number = blacker (air, fat). Same substances read the same way on a plain film. |
| The WINDOW | A pre-selected RANGE of Hounsfield numbers (e.g. −100 to +300) spread over the available gray scale. It is a DISPLAY choice, so POST-PROCESSING can re-window the same scan to show different pathology WITHOUT repeating the study or re-exposing the patient. |
| Units | Radiation is measured in milliSieverts (mSv) and milliGrays (mGy). One gray = one joule per kilogram. For x-ray radiation, 1 mSv = 1 mGy. |
| Term | What you need to know |
|---|---|
| T2: water is WHITE | High water content is BRIGHT — fat, edema, infection, blood (hyperemia), cerebrospinal fluid. Low water content is dark gray. |
| T1: water is DARK | Exactly the inverse. High water content is DARK; low water content is BRIGHT (white). Same list of tissues, opposite appearance. |
| How to check yourself | Look at the ventricles. Bright CSF = T2. Dark CSF = T1. |
| Term | What you need to know |
|---|---|
| Projections are named for THE BEAM | From what it strikes FIRST to the most distal portion. Posterior-anterior = beam enters the back, exits the front. |
| Why PA is preferred | REDUCES MAGNIFICATION OF THE HEART, so cardiomegaly is not misread (the heart is anterior, so on PA it sits near the detector). Also: lower dose to radiation-sensitive organs, maximum lung visualization, better apices, posterior ribs well seen. |
| Standard chest exam | PA AND LATERAL, READ TOGETHER. PA is viewed as if the patient stood in front of you — THEIR RIGHT ON YOUR LEFT. On the lateral the patient faces LEFT. Comparison films are “old gold”: old PA beside new PA, old lateral beside new lateral. |
| Position → indication | DECUBITUS = PLEURAL EFFUSION (gravity levels the fluid out). KUB = supine, AP, genitourinary tract. ABDOMINAL SERIES = STANDING, AP, gastrointestinal tract — air-fluid levels, free air, small bowel obstruction, perforation, volvulus. |
| Three planes | AXIAL (transverse) = upper/lower, much the commonest. CORONAL = anterior/posterior. SAGITTAL = right/left; in the midline it is MIDSAGITTAL (median), off to either side PARASAGITTAL. |
| Cross-sectional viewing convention | CT/MRI/nuclear: patient SUPINE, transverse sections viewed AS IF LOOKING AT THE PATIENT'S FEET — so the PATIENT'S LEFT IS ON THE READER'S RIGHT. Note this is the OPPOSITE of how a PA chest film is oriented. |
| Ultrasound indicator — “crucial” | Cardiac imaging: indicator on the RIGHT of the screen. EVERY other ultrasound: on the LEFT. Get it wrong and left and right are mirrored. |
| Term | What you need to know |
|---|---|
| The highest emitters | Marked IMPORTANT in the deck: CT, PET and SPECT are the HIGHEST-EMITTING medical imaging devices currently in existence. Ultrasound and MRI emit NONE. |
| Organ doses (SLIDE 21 — an IMAGE; the text extracts as EMPTY) | Dental 0.005 · PA chest 0.01 · lateral chest 0.15 · screening mammography 3 · ADULT abdominal CT 10 · barium enema 15 · NEONATAL abdominal CT 20 (mGy or mSv). FOUR ORDERS OF MAGNITUDE across the table. |
| The neonatal point | Neonatal abdominal CT doses TWICE the adult study. Smaller patient, larger organ dose for the same scan — which is exactly why the diagnostic approach asks whether something with less radiation would do. |
| Nuclear medicine is different in KIND | The tracer is inside the patient, so for a while THE PATIENT IS THE SOURCE and can briefly expose other people. No other modality does this. |
| Term | What you need to know |
|---|---|
| CT intravenous — Omnipaque (iohexol) | IODINATED and RADIOPAQUE, not radioactive (the slide’s “radioactive form of iodine” is wrong; only nuclear medicine tracers are radioactive). NEPHROTOXIC → CHECK BUN AND CREATININE, give 1 L NORMAL SALINE to protect the kidneys. For inflammation, cancer staging, tumor delineation, vasculopathy, emboli, thrombi, stenosis, aneurysm. |
| CT oral — barium or Gastrografin | BARIUM IS CONTRAINDICATED IF PERFORATION IS SUSPECTED — it is toxic to extra-intestinal tissue and causes alkaline burns. USE GASTROGRAFIN instead. For the intraluminal space, upper esophagus to rectum. |
| MRI — gadolinium | Assess BUN and creatinine regardless, but it is NOT as harmful as CT contrast; renal function matters mainly for clearance. For CNS tumors (typically characterized WITHOUT biopsy), metastases, soft tissue masses, arthrograms. MRA and MRV are done WITHOUT contrast. |
| PET — fluorodeoxyglucose-18 | NO contraindications, NOT known to be nephrotoxic. May cause HYPERGLYCEMIA. Renally cleared, so the genitourinary tract is ALWAYS contrast positive. |
| SPECT — technetium-99 | Travels to areas of higher blood flow and cellular activity. Bone scans, myocardial perfusion, functional brain imaging, immunoscintigraphy, sentinel node, white cell uptake. Allergic reactions RARE, NO organ damage documented. |
| SHELLFISH IS NOT IODINE | There should be NO CROSS-REACTIVITY between shellfish allergy and iodinated radiocontrast. The real high-risk marker is a documented ANAPHYLACTIC REACTION TO ANY MEDICATION. Pre-treatment exists when contrast is necessary. |
| The stated takeaway | ALWAYS ASK ABOUT ALLERGIES AND ASSESS KIDNEY FUNCTION. The deck also calls contrast “technically radioactive” and carcinogenic: NOT TRUE. Contrast is radiopaque, not radioactive; the CANCER risk is the IONIZING RADIATION of the x-ray-based study. |
| Other routes | Joints = arthrogram. Central nervous system = intrathecal. Bladder = retrograde pyelogram. |
| Term | What you need to know |
|---|---|
| They have not seen the patient | Whatever clinical information you give is what guides the read. A vague report is a CONVERSATION — contact the radiologist and discuss the patient. |
| Unsure which study? | Tell them WHAT YOU ARE LOOKING FOR and they can guide the choice. |
| Multiple regions = multiple orders | MRI brain, C-spine, T-spine and L-spine is FOUR requests, not one. |
| Term | What you need to know |
|---|---|
| NOT on the exam (her words) | Keeping a patient on the SAME MRI machine so serial studies stay comparable — e.g. repeating scans every 6 months in multiple sclerosis. “This is not gonna be on the test.” The ONLY de-emphasis in the whole lecture. |
| Know the VIEW before you read the film | “You need to know what the view is… so that you can decide, is this actually cardiomegaly or not?” A sick inpatient who cannot stand gets an AP — so read AP as AP, or you will call cardiomegaly that is not there. |
| Her named BUZZWORD | FREE AIR UNDER THE DIAPHRAGM = PERFORATED BOWEL. Unless recent laparoscopic surgery with insufflation and unabsorbed gas. Belly pain + fever + nausea/vomiting + no recent surgery → perforation. The abdominal film is UPRIGHT so air rises and fluid settles. |
| Gadolinium vs iodinated — WHY you check renal function | IODINATED contrast is NEPHROTOXIC. GADOLINIUM is mostly a CLEARANCE problem — if kidney function is low it BUILDS UP IN TISSUES and that is toxic. Different reason, same action: “MRI, CT, kidney function, check it.” |
| Shellfish vs iodine allergy — the refinement | NO cross-reactivity between shellfish allergy and iodinated contrast. BUT a genuine IODINE allergy IS a concern. Ask directly: “do you have an iodine allergy, yes or no?” WHEN IN DOUBT, PRETREAT — diphenhydramine and prednisone at intervals beforehand, plus fluids. |
| Why contrast shows a malignancy | Neoplasms GROW THEIR OWN VESSELS and become more vascularized than surrounding tissue, so “that tumor's gonna light up when it's malignant.” Same logic for an abscess: inflammation, edema and increased blood flow. |
| Choosing a modality when you are not sure | Reason from the TISSUE, not from a memorized protocol. BONE → x-ray or CT. SOFT TISSUE → often start with ultrasound. |
| Decubitus is a CHOICE of side | Pick the side based on WHICH DIRECTION YOU WANT THE FLUID TO RUN. Used a lot to layer out fluid. |
| Contrast in pregnancy, primary care | “You should never ever order that… you better have sent them to a specialist. Very dangerous.” |
| Term | What you need to know |
|---|---|
| The four test-selection factors | COST · AVAILABILITY · INVASIVENESS · DIAGNOSTIC YIELD. And the closing rule: ALWAYS CHOOSE THE LEAST INVASIVE TEST THAT ANSWERS THE CLINICAL QUESTION. |
| Which test for which question | INFECTION → potassium hydroxide or culture. NEOPLASM or PERSISTENT RASH → biopsy. ABSCESS vs CELLULITIS → point-of-care ultrasound. |
| KOH readings — the whole table | NEGATIVE: no fungal elements. BRANCHING SEPTATE HYPHAE = DERMATOPHYTE. PSEUDOHYPHAE + BUDDING YEAST = CANDIDA. “SPAGHETTI AND MEATBALLS” = TINEA VERSICOLOR. |
| KOH procedure numbers | 20% potassium hydroxide, ONE drop. Survey at 10× with the CONDENSER LOWERED to reduce illumination (that is what makes epithelial cells visible), then 40× for anything suspicious. Blot excess with GAUZE. Sensitivity depends on ADEQUATE SCRAPING. |
| Biopsy techniques | SHAVE: raised epidermal lesions, basal and squamous cell carcinoma, superficial rashes. PUNCH: FULL-THICKNESS, inflammatory rashes and small lesions. EXCISIONAL: entire lesion, PREFERRED FOR SUSPECTED MELANOMA. |
| THE MELANOMA RULE — she said it three times | NARROW EXCISIONAL BIOPSY, 1–3 mm MARGINS, to a depth that AVOIDS TRANSECTING THE BASE so BRESLOW DEPTH can be measured. NOT a shave. NOT a punch. Acceptable excisional methods: fusiform/elliptical, punch, deep shave/saucerization — ALL must go BELOW the lesion. |
| 1–3 mm vs 0.5–2 cm — do not mix these up | 1–3 MILLIMETERS is the DIAGNOSTIC biopsy margin here in PDM. 0.5–2 CENTIMETERS is the definitive RE-EXCISION margin in CMS I Lecture 9. Different procedure, different purpose. |
| When a partial shave is allowed | ONLY WHEN SUSPICION IS LOW — and it MAY UNDERESTIMATE BRESLOW DEPTH. Facial, acral and very large lesions are named here. |
| Breslow / T categories | Tis = IN SITU. T1 ≤1 mm. T2 >1 to 2 mm. T3 >2 to 4 mm. T4 >4 mm. T is DEPTH IN MILLIMETERS, not width. |
| Biopsy limitations | SAMPLING ERROR, and procedural risks of BLEEDING, SCARRING, INFECTION. She added: THE TECHNIQUE ITSELF DETERMINES HOW EASILY THE SPECIMEN CAN BE EVALUATED. |
| Term | What you need to know |
|---|---|
| POCUS — cellulitis vs abscess | CELLULITIS: dermal thickening, increased echogenicity, COBBLESTONING (footnoted as non-specific — VENOUS STASIS does it too). ABSCESS: HYPOECHOIC/heterogeneous collection, possible debris or septations, POSTERIOR ACOUSTIC ENHANCEMENT. |
| ★ THE RED FLAG she bolded AND said aloud | HYPOTENSION + WHITE BLOOD CELL COUNT ≥15,000 + VIOLACEOUS (purple) SKIN → MUST be screened for NECROTIZING FASCIITIS. Her framing: a patient who looks TOO SICK FOR A SKIN INFECTION. |
| When to escalate past ultrasound | DEEP-SPACE INFECTION · NECROTIZING INFECTION · FOREIGN BODY · GAS. CONTRAST MRI BEST DEFINES THE EXTENT OF TISSUE DAMAGE. |
| Skin/wound culture indications | PURULENT LESIONS — pus from abscesses, carbuncles, furuncles. Empiric treatment WITHOUT culture is reasonable in TYPICALLY PRESENTING, UNCOMPLICATED cases. DO NOT CULTURE AN INFLAMED EPIDERMOID CYST. |
| Culture a chronic wound when | IMMUNOCOMPROMISED · MRSA SUSPECTED · TREATMENT FAILURE. |
| THE LEVINE METHOD | Clean with STERILE WATER OR SALINE, NOT AN ANTIMICROBIAL. Identify 1–2 cm of CLEAN wound tissue. ROTATE the applicator FIVE SECONDS with enough pressure to EXPRESS FLUID. DO NOT sample EXUDATE, ESCHAR or NECROTIC MATERIAL. |
| Culture: advantage vs limits | ADVANTAGE: organism identification PLUS SUSCEPTIBILITIES. LIMITS: superficial swabs prone to CONTAMINATION AND COLONIZATION, may NOT correlate with deep infection. Complex wounds (diabetic foot, pressure ulcers) → DEEPER TISSUE BIOPSY OR ASPIRATE gives higher yield. |
| Term | What you need to know |
|---|---|
| VVEEPP | VISUAL ACUITY · VISUAL FIELDS · EXTERNAL EXAM · EXTRAOCULAR MOVEMENTS · PUPILS · PRESSURE. |
| Visual acuity | INDICATION: EVERY EYE COMPLAINT. Snellen DISTANCE, Rosenbaum NEAR. Test BEST-CORRECTED; add PINHOLE if reduced. UNILATERAL loss → optic nerve/ocular. BILATERAL → systemic/intracranial. |
| Pinhole | Blocks PERIPHERAL light, focuses CENTRAL rays on the retina. CORRECTS → REFRACTIVE. DOES NOT CORRECT OR WORSENS → EYE PATHOLOGY. |
| Visual field patterns | CENTRAL SCOTOMA → macula/optic nerve. PERIPHERAL LOSS → GLAUCOMA. BITEMPORAL HEMIANOPIA → CHIASMAL (pituitary). HOMONYMOUS HEMIANOPIA → RETROCHIASMAL (?stroke). Bedside = CONFRONTATION; formal = PERIMETRY or AMSLER GRID. |
| Fluorescein | Cobalt-BLUE light, AFTER a topical anesthetic. LINEAR → ABRASION. BRANCHING/DENDRITIC → HERPETIC KERATITIS. FIXED DENSE STAINING or OPACITY → ULCER, URGENT REFERRAL. Indications: eye pain, foreign-body sensation, trauma, contact lenses, red eye. |
| Tonometry | Normal intraocular pressure 10–21 mm Hg. ACUTE ANGLE-CLOSURE GLAUCOMA IS AN OPHTHALMOLOGIC EMERGENCY. PRESSURE ALONE IS INSUFFICIENT — most OPEN-ANGLE glaucoma has NORMAL pressure, and readings vary with CORNEAL THICKNESS. |
| Optic disc cupping | Normal cup-to-disc ~0.3; GLAUCOMATOUS >0.7. Glaucomatous disc is EXCAVATED, NOT MERELY PALE — that is what separates it from other optic atrophies. Lamina cribrosa collapse. |
| Ocular hypertension vs glaucoma | OCULAR HYPERTENSION = raised pressure, NO optic damage, NORMAL fields — a RISK FACTOR. GLAUCOMA = raised pressure WITH OPTIC NERVE DAMAGE. |
| Term | What you need to know |
|---|---|
| Rapid strep vs throat culture | RADT: fast, point-of-care, SENSITIVITY ONLY 70–90% → FALSE NEGATIVES. CULTURE: GOLD STANDARD, highest sensitivity, but DELAYED 24–48 HOURS. |
| The two pearls | A NEGATIVE RADT IN A CHILD should be confirmed by CULTURE — NOT routinely required in adults. DO NOT USE ANTISTREPTOCOCCAL ANTIBODY (ASO) TITRES to diagnose ACUTE pharyngitis. |
| Audiometry | Quantifies DEGREE AND TYPE — CONDUCTIVE vs SENSORINEURAL — AFTER abnormal physical exam. Indications: suspected/confirmed loss, PERSISTENT otitis media with effusion, ASYMMETRIC loss (to screen for RETROCOCHLEAR pathology). |
| The two audiometry numbers | AIR–BONE GAP ≥10 dB correlates with MIDDLE-EAR FLUID. Primary-care FAIL = >20 dB HL at ≥1 FREQUENCY. |
| Pure tone audiometry | Screening presents at UPPER LIMITS OF NORMAL: 25–30 dB ADULTS, 15–20 dB CHILDREN. THRESHOLD = softest sound heard at each frequency 50% OF THE TIME. Audiogram: INTENSITY on the VERTICAL axis; RIGHT = RED CIRCLE, LEFT = BLUE X. Bone conduction vibrates through FOREHEAD or MASTOID. WE LOSE HIGH FREQUENCIES FIRST (presbycusis). |
| Tympanometry mechanics | Varies AIR PRESSURE IN THE EXTERNAL CANAL, measures REFLECTED ENERGY. THE LESS COMPLIANT THE SYSTEM, THE GREATER THE INTENSITY REFLECTED BACK. Pressure = HORIZONTAL axis, compliance = VERTICAL. Normal peak 50 mm H2O. |
| TYMPANOGRAM TYPES | A = NORMAL (also typical of SENSORINEURAL loss with a normal middle ear). B = RESTRICTED MOBILITY. C = SIGNIFICANT NEGATIVE PRESSURE (eustachian tube dysfunction), significant for treatment BELOW −200 mm H2O. AS = normal pressure, REDUCED mobility (S = stiff/shallow; ossicular fixation, tympanosclerosis). AD = normal pressure, HYPERmobility (flaccid membrane, disarticulation). |
| The flat tympanogram split | FLAT + HIGH CANAL VOLUME → PERFORATION or PATENT TUBE. FLAT + NORMAL VOLUME → MIDDLE-EAR EFFUSION. That one number is the whole difference. |
| _skip_ — she said she will NOT ask this | The ANIMAL HEARING RANGES figure. Verbatim at 1:00:43: “I’m not going to ask you to be like, what is the range of the killer whale.” It is there to show how wide human hearing is, nothing more. |
| Term | What you need to know |
|---|---|
| CT vs MRI — the two pearls | THINK CT FOR BONE, TRAUMA AND SPEED. THINK MRI FOR SOFT TISSUE, NERVES, AND TUMOR OR INTRACRANIAL EXTENSION. |
| Contrast CT strengths | FIRST-LINE FOR MOST ACUTE HEAD AND NECK INFECTIONS. Shows ABSCESS, EDEMA, GAS, BONE EROSION. Strengths: calcification/bone, sinuses, ACUTE TRAUMA and ORBITAL FRACTURES, FOREIGN BODIES, and the UNSTABLE OR CLAUSTROPHOBIC patient. |
| MRI strengths | SUPERIOR SOFT-TISSUE CONTRAST, NO IONIZING RADIATION, INTRACRANIAL/ORBITAL EXTENSION, PERINEURAL SPREAD, SKULL BASE, TUMORS. |
| NO IMAGING NEEDED | UNCOMPLICATED ACUTE RHINOSINUSITIS · OTITIS · SIMPLE SOFT-TISSUE INFECTIONS. |
| Emergency imaging triggers | FACIAL SWELLING · PROPTOSIS · EYE SIGNS · NEURO SIGNS → contrast CT of SINUSES AND ORBITS. Also complicated sinusitis or orbital cellulitis. |
| Neck mass vs deep neck infection | NECK MASS → ULTRASOUND FIRST (superficial/cystic vs solid, size, VASCULARITY on Doppler). DEEP NECK INFECTION → CONTRAST CT NECK, and the deck says ULTRASOUND IS NOT HELPFUL. Do not swap these. |
| Deep neck infection — the 3 questions | Is there a DRAINABLE ABSCESS · is the AIRWAY compromised · is it SPREADING TOWARDS THE MEDIASTINUM. |
| MRI adds value for | INTRACRANIAL EXTENSION · VASCULAR THROMBOSIS (LEMIERRE) · OSTEOMYELITIS. |
| Acoustic neuroma | MRI WITH CONTRAST — for suspected acoustic neuroma or ASYMMETRIC SENSORINEURAL HEARING LOSS. |
| CT findings by region | SINUS: mucosal thickening, AIR-FLUID LEVELS, opacification. ORBIT: orbital cellulitis with FAT STRANDING, abscess, BLOWOUT FRACTURE, herniated orbital contents. NECK: abscess as a RIM-ENHANCING fluid collection, enlarged or NECROTIC nodes. |
| Blow-out vs tripod fracture | BLOW-OUT: air in the orbit (ORBITAL EMPHYSEMA), fracture of the ORBITAL FLOOR, soft tissue extending into the TOP OF THE MAXILLARY SINUS. TRIPOD: DIASTASIS OF THE FRONTOZYGOMATIC SUTURE + orbital floor fracture with emphysema + fracture through the LATERAL WALL of the maxillary sinus (filled with blood). |
| Term | What you need to know |
|---|---|
| ★ THE DECK DISAGREES WITH ITSELF — 3 values | LYMPHOCYTES: reference table 25–33%, teaching slide 24–44%. PLATELETS: table 150,000–400,000, slide 150,000–450,000. RDW: table 11–15%, slide 12–15%. A FOURTH set is on the labeled smear (slide 15) and matches neither. Everything else agrees across both. |
| With vs without differential | WITHOUT: red cell count, red cell indices, TOTAL white count, platelets — for SCREENING/MONITORING anemia, leukocytosis/leukopenia, thrombocytopenia. WITH: adds NEUTROPHILS, LYMPHOCYTES, MONOCYTES, EOSINOPHILS, BASOPHILS — when the SPECIFIC LINE matters. |
| Which line for which problem | BACTERIAL → NEUTROPHILS. VIRAL → LYMPHOCYTES. ALLERGY/PARASITES → EOSINOPHILS. |
| White cell count | NORMAL 4,500–11,000 cells/μL. LEUKOPENIA below, LEUKOCYTOSIS above. |
| Granulocyte vs agranulocyte | GRANULOCYTES (neutrophil, eosinophil, basophil): DISTINCTIVE CYTOPLASMIC GRANULES with enzymes, proteins, toxic substances. AGRANULOCYTES (monocyte, lymphocyte): NO granules, NON-LOBULAR nucleus. |
| Neutrophils | 54–62%, MOST ABUNDANT. 3–4 LOBED nucleus, granular cytoplasm. AKA polys, PMNs, segs. MAIN DEFENSE AGAINST BACTERIA by PHAGOCYTOSIS. |
| Bands & LEFT SHIFT | BANDS = IMMATURE NEUTROPHILS, normal ≤5%, ONE OR TWO lobes separated by a THICK CHROMATIN BAND. NEUTROPHILS + BANDS = BACTERIAL INFECTION. LEFT SHIFT = increase in IMMATURE cells — neutrophils are CONSUMED faster than they can be replaced. |
| Neutrophils UP | Bacterial infection · MYOCARDIAL INFARCTION · burns · STEROIDS · rheumatoid arthritis · physiologic (PREGNANCY/LABOR, SURGERY). |
| Neutrophils DOWN | Bone marrow damage · FOLATE AND B12 DEFICIENCY (both needed for MARROW FUNCTION) · radiation · TOXIC CHEMICALS (BENZENE) · OVERWHELMING infection · viral (MONONUCLEOSIS, HIV, HEPATITIS). |
| Why steroids raise neutrophils | DEMARGINATION — they cause neutrophils to DETACH FROM THE BLOOD VESSEL WALL and enter the main bloodstream. Not increased production. |
| Eosinophils / Basophils | EOS 1–3%, TWO-LOBED, granules contain HISTAMINES. Up: PARASITES, ALLERGY, CANCER. BASO <1%, usually two-lobed, granules contain HEPARIN + histamine. Up: allergy, cancer. A NORMAL COUNT CAN BE ZERO for both. |
| Monocytes / Lymphocytes | MONO 3–7%, LARGEST white cell, NO granules → MACROPHAGES or DENDRITIC CELLS (KUPFFER in liver, ALVEOLAR in lung, LANGERHANS in skin). Up: chronic inflammation, stress, viral. LYMPH: small, mononuclear, no granules; T, B and NK cells — THE CBC DOES NOT TELL THEM APART. Up: VIRAL. Down: HIV. |
| Cell lifespans (image-only) | NEUTROPHIL 7 HOURS · EOSINOPHIL 8–12 DAYS · BASOPHIL a few hours to a few days · MONOCYTE 3 DAYS · B and T MEMORY CELLS MAY LIVE FOR YEARS. |
| Term | What you need to know |
|---|---|
| ★ ABSOLUTE NEUTROPHIL COUNT | ANC = WBC × (%NEUTROPHILS + %BANDS) ÷ 100. BANDS COUNT WITH THE NEUTROPHILS — that is the trap. Alternative form when WBC is in thousands: 10 × WBC(thousands) × (%neuts + %bands). |
| The deck's worked example | 6,000/μL with 40% neutrophils and 5% bands → 6,000 × 45 ÷ 100 = 2,700/μL. NOTE the slide prints “6,000 x (40 + 5/100)” which evaluates to 240,300 — the BRACKETS are a typo, the ANSWER of 2,700 is right. |
| ★ NEUTROPENIA GRADES (image-only) | MILD 1,000 to <1,500 cells/μL. MODERATE 500 to <1,000. SEVERE <500. NOT IN THE SLIDE TEXT AT ALL. |
| General absolute count | ANY line: TOTAL WBC × THAT TYPE'S PERCENTAGE ÷ 100. A percentage means nothing without the total. |
| Platelets | From MEGAKARYOCYTES in the BONE MARROW, break into FRAGMENTS — so NOT REALLY CELLS. Lifespan 7–10 DAYS. PRIMARY ROLE HEMOSTASIS. HEMORRHAGE RISK INCREASES BELOW 20,000. |
| Platelets UP / DOWN | UP: trauma, acute hemorrhage, IRON DEFICIENCY, polycythemia vera. DOWN: MARROW SUPPRESSION — chemo, alcohol, radiation, aplastic anemia, drugs. Note IRON DEFICIENCY RAISES PLATELETS WHILE LOWERING RED CELLS. |
| Mean platelet volume | 7.5–12.5 fL, AVERAGE SIZE of platelets, a marker of FUNCTION AND ACTIVATION. UP = increase in IMMATURE platelets (recent blood loss). DOWN = bone marrow failure. |
| Hemoglobin vs hematocrit | HEMOGLOBIN = amount of hemoglobin in a VOLUME of blood. HEMATOCRIT = PERCENTAGE of blood that is red cells (packed cell volume). RULE OF THUMB: HEMOGLOBIN × 3 = HEMATOCRIT. |
| The three that raise ALL of RBC/Hgb/Hct | POLYCYTHEMIA VERA · CHRONIC HYPOXIA (COPD, sleep apnea, high altitude) · DEHYDRATION. Hematocrit adds SMOKING and HYPOVENTILATION; its decreased list adds HEMOLYSIS. |
| ★ THE FOUR INDICES | MCV = Hct(%) × 10 ÷ RBC — average VOLUME, 80–100 fL, MEASURED. MCH = Hgb × 10 ÷ RBC — hemoglobin PER CELL, 27–33 pg. MCHC = Hgb × 100 ÷ Hct — CONCENTRATION in packed cells, 32–36 g/dL. RDW = degree of ANISOCYTOSIS. MCH AND MCHC DIFFER ONLY IN THE DENOMINATOR. |
| MCHC's special job | AUTOMATED SCREENING FLAG for HEREDITARY SPHEROCYTOSIS and other HYPERCHROMIC/DEHYDRATED red cell states. |
| Hypo / normo / hyperchromic | HYPOchromic: central pallor >1/3 of the diameter, MCH <27, MCHC <32 — iron deficiency, thalassemia. NORMOchromic: pallor EXACTLY 1/3. HYPERchromic: MCH >33, MCHC >36 — SPHEROCYTES. |
| The red cell COUNT caveat | It DOES NOT accurately measure OXYGEN CARRYING CAPACITY and is NOT directly used to diagnose anemia — though still used to evaluate it. |
| Term | What you need to know |
|---|---|
| The four categories | SIZE · HEMOGLOBIN DISTRIBUTION · SHAPE VARIATION (POIKILOCYTOSIS) · INCLUSIONS AND CELL DISTRIBUTION. |
| ★ ACANTHOCYTE vs ECHINOCYTE | ACANTHOCYTE (spur, “acantha” = thorn): IRREGULAR spikes, NO central pallor → LIVER DISEASE. ECHINOCYTE (burr, sea urchin): REGULARLY distributed, LESS POINTED tips, CENTRAL PALLOR PRESERVED → RENAL DISEASE. Two features, two diseases. |
| Schistocytes | FRAGMENTED red cells — helmet, horn, TRIANGULAR, MICROSPHEROCYTE (last two are IMAGE-ONLY). Usually MICROCYTIC, LACK central pallor. HEMOLYSIS, MECHANICAL TRAUMA (mechanical heart valves), MEDICATIONS (CYCLOSPORINE). ★ AUTOMATED COUNTERS MAY COUNT THEM AS PLATELETS. |
| Sickled cell (drepanocyte) | THIN CRESCENT, NO central pallor, DENSE hemoglobin so NORMOCHROMIC TO HYPERCHROMIC. Forms UNDER LOW OXYGEN TENSION, causes SLUDGING in tissues. |
| Spherocyte | PERFECTLY ROUND, LOSS OF CENTRAL PALLOR, often SMALLER than normal → HEREDITARY SPHEROCYTOSIS (mostly INHERITED; shortens red cell life). |
| Target cell (codocyte) | DARK CIRCLE INSIDE the central pallor = BULLSEYE. Due to REDUNDANT CELL MEMBRANE. POST SPLENECTOMY and LIVER DISEASE. |
| Teardrop cell (dacrocyte) | Formed in BONE MARROW INFILTRATED BY SCAR TISSUE OR CANCEROUS CELLS → BONE MARROW DISEASE. |
| Basophilic stippling | BLUE-BLACK dots of RIBOSOMAL RNA, EVENLY DISTRIBUTED through the cytoplasm → LEAD POISONING. The even distribution is the discriminator. |
| Howell-Jolly body | A SINGLE dot-like DARK PURPLE RESIDUAL NUCLEAR FRAGMENT → POST SPLENECTOMY. Normally REMOVED BY THE SPLEEN, so finding one means SPLENIC DYSFUNCTION OR ASPLENIA. Target cells appear in the same field. |
| ★ HEINZ BODIES — the easiest thing to miss | DENATURED HEMOGLOBIN at the PERIPHERY of the cell → G6PD DEFICIENCY. THEY REQUIRE A SUPRAVITAL STAIN (NEW METHYLENE BLUE) — INVISIBLE ON THE ROUTINE WRIGHT STAIN, so nobody reports them unless you ask. This fact is ONLY inside the figure. |
| Rouleaux vs agglutination | ROULEAUX: STACKED IN CHAINS, “ROWS OF COINS” — RAISED SERUM PROTEINS NEUTRALIZE the red cells' NEGATIVE SURFACE CHARGE → MULTIPLE MYELOMA, LIVER DISEASE. AGGLUTINATION: DISORDERLY CLUMPING — ANTIBODIES COAT and BRIDGE the cells → TRANSFUSION REACTIONS. |
| Term | What you need to know |
|---|---|
| The four evaluation steps | ASSESS CLINICAL PRESENTATION · CHECK CBC AND CHEMISTRY PANEL · DETERMINE THE MCV · CHECK THE RETICULOCYTE COUNT. Do them SIMULTANEOUSLY. Look at the PERIPHERAL SMEAR if you can get one. |
| Reticulocyte count | Tells you whether the BONE MARROW IS FUNCTIONING. Most helpful when VERY ELEVATED OR VERY DECREASED. DECREASED = UNDERPRODUCTION. INCREASED = HEMOLYSIS OR BLOOD LOSS. |
| ★ THE THREE MCV BANDS | MICROCYTIC <80 fL · NORMOCYTIC 80–100 fL · MACROCYTIC >100 fL. Hemoglobin says there IS an anemia; MCV says WHICH ALGORITHM TO RUN. |
| Microcytic causes | IRON DEFICIENCY (MOST COMMON CAUSE OF ANEMIA — MUST EVALUATE FOR OCCULT BLOOD LOSS, often the FIRST SIGN OF GI BLEEDING) · LEAD POISONING · ANEMIA OF CHRONIC DISEASE · THALASSEMIA · SIDEROBLASTIC ANEMIA. |
| ★ IRON STUDIES — the two patterns | IRON DEFICIENCY: FERRITIN ↓, IRON ↓, TIBC ↑. ANEMIA OF CHRONIC DISEASE: FERRITIN ↑, IRON ↓, TIBC ↓. Ferritin is an ACUTE PHASE REACTANT, so it RISES in inflammation even though the iron is unavailable. |
| All three normal in a microcytic anemia | → Is there BASOPHILIC STIPPLING? YES → obtain SERUM LEAD. NO → THALASSEMIA TRAIT. |
| Iron comparison table (image-only) | THALASSEMIA MINOR is the row where the MCV IS LOW AND EVERYTHING ELSE IS NORMAL. INFLAMMATORY ANEMIA is the one with a NORMAL MCV. THALASSEMIA MAJOR and SIDEROBLASTIC both have LOW MCV with RAISED FERRITIN. |
| Iron transport analogy | BUS = TRANSFERRIN (transports). BUS STOP = FERRITIN (stores; MEASURABLE because it is outside the marrow). HOME = HEMOSIDERIN (CANNOT be measured). % SATURATION = TIBC (how many can sit on the bus). SCHOOL = the RED BLOOD CELL. |
| Macrocytic — megaloblastic vs not | MEGALOBLASTIC: B12, FOLATE, DRUGS IMPAIRING DNA SYNTHESIS (METHOTREXATE, ANTIRETROVIRALS, HYDROXYUREA), COPPER. NON-MEGALOBLASTIC: ALCOHOL, LIVER DISEASE, HYPOTHYROIDISM, RETICULOCYTOSIS, primary marrow disorders, chronic kidney disease. |
| The megaloblastic smear finding | MACROOVALOCYTES + HYPERSEGMENTED NEUTROPHILS. WITHOUT them → CHRONIC LIVER DISEASE or ACUTE HEMATOLOGIC MALIGNANCY. |
| Normocytic — the split | HYPO-PROLIFERATIVE: aplastic anemia, anemia of chronic disease, MARROW INFILTRATION BY TUMOR, hypometabolic states. HEMOLYSIS/HEMORRHAGE: acute blood loss (HGB AND HCT START TO FALL WITHIN 2–3 DAYS), intrinsic and extrinsic hemolytic anemia, sickle cell. |
| Intrinsic vs extrinsic hemolysis | INTRINSIC = a DEFECT IN THE RED CELL causing PREMATURE SPLENIC REMOVAL. EXTRINSIC = MECHANICAL STRESS, IMMUNOLOGIC DESTRUCTION or INFLAMMATORY INJURY FROM OUTSIDE. |
| ★ The normocytic reticulocyte split | HIGH RETICS → HEMOLYSIS, SICKLE CELL, ACUTE HEMORRHAGE. LOW RETICS + LOW WBC/PLATELETS → LEUKEMIA, METASTATIC MALIGNANCY, APLASTIC ANEMIA. LOW RETICS + NORMAL/HIGH WBC/PLATELETS → CHRONIC INFECTION/INFLAMMATION, MALIGNANCY, CHRONIC RENAL DISEASE, ENDOCRINE DYSFUNCTION. |
| Two things in the algorithm people walk past | IRON DEFICIENCY APPEARS IN BOTH THE MICROCYTIC AND THE NORMOCYTIC BRANCH — which is why iron studies are obtained even with a normal MCV. And in the microcytic branch obtain IRON STUDIES IN ALL INDIVIDUALS, because CONCOMITANT IRON DEFICIENCY CAN AFFECT HEMOGLOBIN ANALYSIS and hide a thalassemia. |
| The fishbone | WBC on the LEFT · HGB ABOVE the center line · HCT BELOW it · PLATELETS on the RIGHT. |
| Term | What you need to know |
|---|---|
| ★ The ranges are MEANT to be approximate | She teaches them as LAB-DEPENDENT BY DESIGN: “54 to 62 PLUS OR MINUS A FEW, depending on what lab you're in… IT DOESN'T MATTER WHAT THE RANGE IS, IT JUST MATTERS WHAT THE RANGE IS FOR WHERE YOU'RE WORKING.” So the deck's three “contradictions” are not errors. Learn the approximate figure and the DIRECTION of abnormality. |
| ★ The exception — PLATELETS | She used 150,000–450,000 and said this is the ONE she has NOT seen vary from lab to lab. If you must commit one platelet range, commit that. |
| ★ ANC — you must be able to calculate it | Apps and the EMR will compute it, “HOWEVER, EVERYONE NEEDS TO KNOW HOW TO CALCULATE THAT.” Two formulas; which one depends ONLY on whether the white count is in whole numbers or thousands. |
| ★ The neutropenia table only applies BELOW 1,500 | Asked directly: the “CHART IS ONLY FOR THOSE INDIVIDUALS who have an ANC of LESS THAN 1500. Because we know that the 2700 is more than 1500, we know that the patient is not neutropenic.” NOT ON THE SLIDE. Calculate FIRST, then decide whether the table applies at all. |
| Where she put the line on the anemia algorithm | TWICE. Microcytic: “for now, I'm HAPPY IF YOU UNDERSTAND GENETIC VERSUS NON-GENETIC; the rest will come later.” Normocytic: “all of this will come [with heme] — if you can just FOCUS ON THIS FIRST PART here.” The full algorithm is still on the slides; that is just where the emphasis is. |
| With vs without differential — her rule | FIRST time you meet a patient and work them up → WITH differential. AFTERWARDS, monitoring a known problem → WITHOUT is enough. And: “IF WE DON'T KNOW WHAT TO ORDER, START WITH A CBC.” |
| Her hemoglobin/hematocrit habit | Read the HEMOGLOBIN, MULTIPLY BY THREE, and check the HEMATOCRIT lands in the same vicinity. |
| Term | What you need to know |
|---|---|
| BASIC metabolic panel — 8 tests | GLUCOSE · CALCIUM · SODIUM · POTASSIUM · CHLORIDE · CO2 (bicarbonate) · BUN · CREATININE. Also called chem-7 or chem-8. |
| CHEM-7 vs CHEM-8 | CALCIUM. The chem-8 has it, the chem-7 does not. That is the whole difference. |
| COMPREHENSIVE panel — 14 tests | All 8 above PLUS ALBUMIN · TOTAL PROTEIN · ALKALINE PHOSPHATASE · ALANINE TRANSAMINASE · ASPARTATE AMINOTRANSFERASE · BILIRUBIN. Also called chem-14. |
| Which panel when | BASIC is enough for ELECTROLYTES, GLUCOSE and RENAL SCREENING. Step up to COMPREHENSIVE when you need LIVER and NUTRITIONAL PROTEIN status. |
| The functional groups | FUEL: glucose. ELECTROLYTES/ACID-BASE: sodium, potassium, chloride, bicarbonate. KIDNEY: BUN, creatinine. MINERAL: calcium. LIVER/PROTEIN (comprehensive only): the six. |
| Two abbreviation traps she called out | Cr = CREATININE, not chromium. BUN = BLOOD UREA NITROGEN, not boron-uranium-nitrogen. And DO NOT ABBREVIATE IN THE ELECTRONIC NOTE — write sodium out. |
| THE RANGES YOU DO NOT HAVE TO MEMORIZE | Her words: “we ALWAYS give you reference ranges.” Learn DIRECTION of abnormality and the rough figure. Sodium “around 140” is the level of detail she asked for. |
| Where this deck contradicts itself | BICARBONATE text 22–29 vs fishbone 22–28 (22–26 in the gas column). GLUCOSE text 70–99 fasting vs fishbone 70–120. BUN text 7–20 vs fishbone 7–18. CREATININE 0.6–1.2 agrees. Nothing is graded on which is right. |
| Why a normal result does not exclude disease | A normal range is the MEAN ± 2 STANDARD DEVIATIONS, so ~2.5% OF HEALTHY PEOPLE fall outside it by chance. |
| Term | What you need to know |
|---|---|
| The four cations and anions | SODIUM = major EXTRAcellular cation. POTASSIUM = major INTRAcellular cation. CHLORIDE = major EXTRAcellular anion. BICARBONATE = primary extracellular BUFFER. |
| THE SODIUM RULE | An abnormal sodium is a WATER PROBLEM FIRST. Ask “too much or too little free water?” BEFORE “too much or too little salt?” Serum sodium reflects WATER BALANCE, not total-body sodium. |
| Who controls what | WATER handling → THIRST and ANTIDIURETIC HORMONE. EXTRACELLULAR VOLUME → total-body sodium via RENIN–ANGIOTENSIN–ALDOSTERONE. |
| Potassium handling | EXCRETED BY THE KIDNEY WITH NO REABSORPTION → must be replaced by DIET or SUPPLEMENT or it drops fast. Driven by ALDOSTERONE at the DISTAL TUBULE and COLLECTING DUCT. |
| What shifts potassium across the membrane | INSULIN · ACID-BASE STATUS · CATECHOLAMINES. This is why the potassium in DKA misleads — serum can be HIGH while TOTAL BODY IS DEPLETED. |
| Potassium ↔ pH — both directions | ACIDOSIS drives K OUT of cells (serum rises). ALKALOSIS drives K IN (serum falls). And K DEPLETION INCREASES RENAL ACID SECRETION. |
| Potassium danger | BOTH hyper- and hypokalemia cause LIFE-THREATENING ARRHYTHMIAS. Small serum changes = large physiological effect. |
| Chloride | Follows SODIUM to preserve ELECTRICAL NEUTRALITY. Useless alone. RECIPROCAL WITH BICARBONATE. LOW Cl + HIGH HCO3 = METABOLIC ALKALOSIS (vomiting). Losing Cl raises the strong ion difference. |
| Bicarbonate | Reported as “CO2” = TOTAL carbon dioxide, mostly bicarbonate. LOW = METABOLIC ACIDOSIS → CALCULATE THE ANION GAP. HIGH = METABOLIC ALKALOSIS. |
| Term | What you need to know |
|---|---|
| THE FORMULA | ANION GAP = SODIUM − (CHLORIDE + BICARBONATE). NORMAL 8–12 mEq/L. She said this aloud: “quick and dirty, calculate your anion gap, and our normal range is 8 to 12.” |
| Extended formula | (SODIUM + POTASSIUM) − (CHLORIDE + BICARBONATE). NORMAL 10–14. Potassium is added to the CATIONS. |
| RAISED gap | Unmeasured ACIDS. MUDPILES: Methanol · Uremia · Diabetic ketoacidosis · Paraldehyde/propylene glycol · Isoniazid/iron · Lactic acidosis · Ethylene glycol · Salicylates. |
| NORMAL gap | BICARBONATE LOSS from GUT or KIDNEY = HYPERCHLOREMIC metabolic acidosis. |
| Albumin correction | ADD ~2.5 to the gap for every 1 g/dL the ALBUMIN HAS FALLEN — albumin is itself an unmeasured anion. |
| WHAT SHE DOES NOT WANT CALCULATED | GLOMERULAR FILTRATION RATE — “I don’t need you to calculate that or know that just yet, but know OF it.” CORRECTED SODIUM — she uses UpToDate/MedCalc. Know WHAT it is for and WHICH WAY it moves. |
| Term | What you need to know |
|---|---|
| BUN | Nitrogenous waste of PROTEIN metabolism. Made by the LIVER, cleared by the KIDNEY. NON-SPECIFIC — also raised by DEHYDRATION, GI BLEEDING, HIGH PROTEIN INTAKE, CATABOLIC STATES. |
| Creatinine | Waste of MUSCLE CREATINE metabolism. Filtered by the kidney. MORE SPECIFIC than BUN. Influenced by MUSCLE MASS, AGE, SEX. |
| THE RATIO | BUN : CREATININE > 20 : 1 = PRERENAL. Below that = INTRINSIC RENAL. |
| The creatinine trap | A NORMAL creatinine can HIDE a reduced filtration rate in the ELDERLY or CACHECTIC — low muscle mass makes less creatinine. |
| INJURY vs FUNCTION — the asterisk on her slide | AST · ALT · ALK PHOS · BILIRUBIN mark liver INJURY. ALBUMIN · PROTHROMBIN TIME · BILIRUBIN measure FUNCTION. |
| AST vs ALT | ALT is MORE liver-specific. AST is ALSO in CARDIAC and SKELETAL MUSCLE, KIDNEY and BRAIN — so a raised AST with a NORMAL ALT points to MUSCLE, not liver. |
| Alkaline phosphatase | CHOLESTASIS / BILE DUCT OBSTRUCTION. Also in BONE, PLACENTA, INTESTINE. CONFIRM HEPATIC ORIGIN WITH GGT. |
| Albumin | Made ONLY by the liver, HALF-LIFE ~3 WEEKS → a LOW albumin means CHRONIC disease (>3 weeks). May also drop in severe illness. |
| Prothrombin time / INR | MOST SENSITIVE FUNCTIONAL MARKER. Can prolong WITHIN 24 HOURS. Factors II, VII, IX, X. |
| The four hepatic patterns | HEPATOCELLULAR: AST/ALT out of proportion to ALP. CHOLESTATIC: ALP out of proportion to AST/ALT. MIXED: both. ISOLATED HYPERBILIRUBINEMIA: bilirubin up, enzymes normal (Gilbert, hemolysis). |
| Three liver shortcuts | AST:ALT > 2:1 = ALCOHOL. AST/ALT IN THE THOUSANDS = only 3 causes — VIRAL, ISCHEMIA, TOXINS. Magnitude: mild <5×, moderate 5–15×, severe >15×. |
| Term | What you need to know |
|---|---|
| RENAL pattern | ↑ BUN · ↑ CREATININE · ↓ FILTRATION RATE · ± ↑ POTASSIUM, ↑ PHOSPHATE, ↓ CALCIUM · METABOLIC ACIDOSIS · ALBUMINURIA. |
| HEPATIC pattern | ↑ AST/ALT (hepatocellular) OR ↑ ALP/BILIRUBIN (cholestatic); ↓ ALBUMIN and ↑ PROTHROMBIN TIME in advanced disease. |
| METABOLIC pattern (DKA) | ↑ GLUCOSE · ↓ BICARBONATE · ↑ ANION GAP · LOW pH · ± ↑ POTASSIUM DESPITE TOTAL-BODY DEPLETION. |
| Two overlaps by name | HEPATORENAL SYNDROME = liver AND kidney failure together. CARDIORENAL SYNDROME = the cardiac equivalent. DKA hits electrolytes and kidney at once. |
| Reading order for an abnormal panel | ELECTROLYTES/ACID-BASE (then the gap) → RENAL (BUN, creatinine, ratio) → GLUCOSE → LIVER → MINERALS. |
| Fluid balance core tests | SERUM SODIUM = water balance. SERUM OSMOLALITY (~275–285) separates TRUE hypotonic from PSEUDO/HYPERTONIC. URINE SODIUM <20 = HYPOVOLEMIA; >40 with concentrated urine = SIADH. BUN:Cr >20 = PRERENAL. |
| THREE PITFALLS | HYPERGLYCEMIA lowers measured sodium ~1.6–2 per 100 mg/dL glucose → CORRECTED SODIUM. PSEUDOHYPONATREMIA from HYPERLIPIDEMIA/HYPERPROTEINEMIA — low sodium with a NORMAL OSMOLALITY. And THE NUMBER ALONE NEVER GIVES THE DIAGNOSIS. |
| Correlating with other tests | ABNORMAL LFTs → ULTRASOUND first. LOW eGFR/ALBUMINURIA → urine studies + renal ultrasound; CHRONIC needs ≥3 MONTHS; CYSTATIN C confirms. DKA → ketones/beta-hydroxybutyrate, venous gas, urinalysis, ECG (for potassium), CBC. HYPONATREMIA → serum osm + urine sodium/osm. |
| THE VOMITING CASE | ↓ Na · ↓ K · ↓ Cl · ↑ HCO3 · ALKALEMIA. WHY IT PERSISTS: volume + K + Cl depletion force the kidney to reabsorb sodium AND bicarbonate. WHAT FIXES IT: SALINE + POTASSIUM CHLORIDE — replacing all three. NOT bicarbonate. |
| Term | What you need to know |
|---|---|
| WHAT IT COVERS | PHYSICAL, CHEMICAL and MICROSCOPIC contents of urine. Complements — does not replace — SERUM CREATININE and BLOOD UREA NITROGEN in a renal workup. |
| ALWAYS ORDER IT FOR | ABDOMINAL, PELVIC or BACK PAIN. Also routine on admission. |
| COLOR — pale/colorless | DILUTE urine, possibly overhydrated. |
| COLOR — dark yellow/amber | CONCENTRATED urine, possibly dehydrated. |
| COLOR — yellow-brown/green | BILIRUBIN → hepatitis, cirrhosis, biliary obstruction. |
| COLOR — bright/dark red | BLOOD. Or food: BEETS, blueberries, rhubarb. |
| COLOR — blue/orange/green | MEDICATIONS. Tell the patient BEFORE they start so it does not alarm them. |
| TRANSPARENCY scale | CLEAR → HAZY → CLOUDY → TURBID. Cloudiness = cells, bacteria, yeast, crystals, mucus, contrast or fat. |
| FOAM | PROTEIN. The one inspection finding that points at a specific pad. |
| ODOR — normal | AROMATIC. |
| ODOR — ammonia | Sample STOOD too long; bacteria decomposed the urea. Refrigerate if not read in 1–2 hours, and add NO preservative. |
| ODOR — foul | Bacterial infection. FECAL odor → enterovesical FISTULA. |
| ODOR — fruity/sweet | KETONES → check the blood sugar. |
| Term | What you need to know |
|---|---|
| SPECIMEN | FRESH, in a STERILE container. Strips stored DESICCATED. |
| TIMING | READING TIME DIFFERS BY ANALYTE — glucose 30 seconds, leukocytes 2 minutes. Cannot be read all at once. |
| MANUFACTURER TRAP | Pads are in DIFFERENT ORDERS on different brands. Read a strip against ITS OWN chart. |
| QUALITATIVE result | Positive or negative. |
| SEMI-QUANTITATIVE result | TRACE / 1+ / 2+ / 3+ — a GRADED ESTIMATE, not a measurement. |
| SHOULD READ NEGATIVE | LEUKOCYTE ESTERASE · NITRITES · KETONES · GLUCOSE · BLOOD · BILIRUBIN. Protein is negative or trace. |
| ALWAYS CARRY A VALUE | SPECIFIC GRAVITY and pH. Neither is ever simply 'negative'. |
| What you are NOT asked | To memorize reference RANGES. If a range is needed it will be given. Know DIRECTION and MEANING. |
| Term | What you need to know |
|---|---|
| WHAT pH REPORTS | The RENAL TUBULES' ability to hold the hydrogen ion concentration steady. |
| HOW the kidney does it | EXCRETES hydrogen ions as AMMONIUM; REABSORBS and PRODUCES bicarbonate. |
| WHAT MOVES IT | DIET · MEDICATIONS · SYSTEMIC ACID-BASE DISORDERS · TUBULAR FUNCTION. |
| ACIDIC urine | Ketoacidosis · E. COLI infection · metabolic and respiratory ACIDOSIS · diet high in MEAT or cranberries. |
| ALKALINE urine | UREA-SPLITTING bacteria (PROTEUS, STAPH, KLEBSIELLA, PSEUDOMONAS) · contamination · acute and chronic renal failure · RENAL TUBULAR ACIDOSIS · metabolic and respiratory ALKALOSIS · diet high in FRUIT and VEG. |
| THE NAME TRAP | RENAL TUBULAR ACIDOSIS gives ALKALINE urine — the defect is a failure to EXCRETE acid. |
| ACIDIC urine stones | CALCIUM OXALATE and URIC ACID. Treat by ALKALINIZING the urine (chiefly for uric acid). |
| ALKALINE urine stones | TRIPLE PHOSPHATE and STRUVITE. Treat the INFECTION — urease-producing bacteria drive them. |
| Term | What you need to know |
|---|---|
| LEUKOCYTE ESTERASE — what | Detects the ESTERASE white cells release. POSITIVE = PYURIA. That is the take-home point. |
| LEUKOCYTE ESTERASE — also raised by | INTERSTITIAL CYSTITIS and GLOMERULONEPHRITIS — inflammatory, not infective. |
| NITRITES — mechanism | UREASE-producing bacteria carry a REDUCTASE that turns urinary NITRATES into NITRITES. |
| NITRITES — the naming point | It is NITRITES, not nitrates. She asked for this twice. |
| NITRITES — time needed | MORE THAN FOUR HOURS in the bladder between voids for the conversion. |
| THE BIG ONE | E. COLI causes MOST urinary tract infections and is RARELY UREASE-POSITIVE. So a POSITIVE nitrite is helpful; a NEGATIVE one DOES NOT rule out infection. |
| NITRITE sensitivity | About 50% — LESS sensitive than leukocyte esterase. |
| EITHER PAD NEGATIVE + symptoms | STILL SEND URINE CULTURE AND SENSITIVITY. |
| PEDIATRIC caveat | Less reliable in young children — they void too often for the conversion. |
| Term | What you need to know |
|---|---|
| KETONES — meaning | Cells are burning FATTY ACIDS instead of GLUCOSE. Made in the LIVER, normally fully metabolized. |
| KETONES — causes | Uncontrolled DIABETES / DKA · STARVATION · FASTING · ALCOHOLIC KETOACIDOSIS · HIGH-FAT LOW-CARB diet · LIVER DISEASE · FEBRILE ILLNESS IN INFANTS AND CHILDREN. |
| KETONES — next move | CHECK THE GLUCOSE. |
| GLUCOSE — why normally none | Filtered freely, then WHOLLY REABSORBED in the PROXIMAL tubules. |
| TUBULAR THRESHOLD | The blood glucose above which the tubules can no longer reabsorb it all — around 180 mg/dL. VARIES BETWEEN PEOPLE, which is why glucosuria is NOT diagnostic. |
| GLUCOSE without high blood sugar | IMPAIRED TUBULAR REABSORPTION · DEXTROSE-containing IV fluids · PREGNANCY (trace is normal, threshold falls). |
| Term | What you need to know |
|---|---|
| WHAT THE PAD DETECTS | HEME — present in RED CELLS, FREE HEMOGLOBIN and MYOGLOBIN alike. A positive result DOES NOT SAY WHICH. |
| HEMATURIA | INTACT RED CELLS. From bleeding ANYWHERE along the urinary tract. |
| HEMATURIA — causes | INFECTION · INFLAMMATION · TRAUMA · TUMOR · CALCULUS · OVER-AGGRESSIVE ANTICOAGULATION. |
| GROSS vs MICROSCOPIC | GROSS is visible to the naked eye. MICROSCOPIC needs analysis — defined as THREE OR MORE red cells. |
| HEMOGLOBINURIA | FREE HEMOGLOBIN, NO intact cells. From INTRAVASCULAR HEMOLYSIS — sickle cell, transfusion reaction, severe BURNS. |
| HEMOGLOBINURIA — the confirming test | RAISED SERUM UNCONJUGATED BILIRUBIN (a direct product of hemoglobin metabolism). |
| MYOGLOBINURIA | MYOGLOBIN, NO intact cells. From SKELETAL MUSCLE injury — trauma, ELECTRIC SHOCK, RHABDOMYOLYSIS (compression, hyperthermia, STATINS). |
| MYOGLOBINURIA — the confirming test | RAISED SERUM CREATINE PHOSPHOKINASE. |
| TRACE blood, well patient | Can follow STRENUOUS EXERCISE. |
| Term | What you need to know |
|---|---|
| BILIRUBIN — which form | CONJUGATED only — it is the WATER-SOLUBLE one. |
| BILIRUBIN — what it means | Disease AFTER conjugation, or BILIARY OBSTRUCTION. Can appear DAYS BEFORE JAUNDICE is visible. |
| PROTEIN — what and what for | ALBUMIN mostly. Reports GLOMERULAR and TUBULAR function. Semi-quantitative. |
| PROTEIN — normal trace | PREGNANCY · FEVER · STRENUOUS EXERCISE ('functional proteinuria'). |
| PROTEIN — false positive | CONTAMINATION with PROSTATIC or VAGINAL secretions. |
| PROTEIN — the four mechanisms | DIMINISHED TUBULAR REABSORPTION (tubular disease, pyelonephritis, interstitial nephritis) · TRANSIENT/MILD (exercise, acute illness, urinary tract bleeding or infection) · GLOMERULAR DAMAGE (nephrotic syndrome, glomerulonephritis, diabetes, polycystic kidney disease, lupus, preeclampsia) · INCREASED SERUM PROTEIN (myeloma). |
| PROTEIN — next test | TWENTY-FOUR HOUR URINE COLLECTION. The strip only estimates. |
| THE MYELOMA TRAP | REAGENT STRIPS ARE INSENSITIVE TO BENCE JONES PROTEINS. Use URINE PROTEIN ELECTROPHORESIS, not a dipstick. |
| PROTEIN is NOT pathognomonic | It narrows the field; it does not name the disease. |
| SPECIFIC GRAVITY — what | WEIGHT of SOLUTES against an equal volume of WATER. Estimates CONCENTRATING and EXCRETORY ability. |
| SPECIFIC GRAVITY — particle SIZE matters | Marbles vs glitter. RADIOGRAPHIC CONTRAST has large particles and drives it ABOVE 1.040. |
| LOW specific gravity (dilute) | OVERHYDRATION · DIURESIS · CHRONIC KIDNEY DISEASE · DIABETES INSIPIDUS (less ADH → more water out). |
| HIGH specific gravity (concentrated) | DEHYDRATION · REDUCED RENAL BLOOD FLOW (heart failure, hypotension, renal artery stenosis) · SIADH (more ADH → less water out). |
| Term | What you need to know |
|---|---|
| MICROSCOPIC urinalysis adds | WHITE CELLS · RED CELLS · SQUAMOUS EPITHELIAL CELLS · CASTS · CRYSTALS. |
| BACTERIA — significant when | Collected by STRAIGHT CATHETERIZATION, or alongside RAISED WHITE CELLS and a POSITIVE LEUKOCYTE ESTERASE. |
| BACTERIA — probably NOT significant when | More than TWENTY SQUAMOUS EPITHELIAL CELLS per high power field (contamination), or from a LONGSTANDING INDWELLING CATHETER (colonization, not acute infection). |
| DEFINITIVE diagnosis | GRAM STAIN and CULTURE. |
| THE WORKED CASE | Dysuria/frequency/urgency + LEUKOCYTE ESTERASE, NITRITES and BLOOD positive; glucose, bilirubin, ketones, protein NEGATIVE → URINARY TRACT INFECTION → send CULTURE AND SENSITIVITY. |