MT POST cheat sheet

Prefixes: hyper- (above normal), hypo- (below normal), tachy- (fast), brady- (slow), leuko- (white), cyto- (cell), nephro- (kidney), hepato- (liver).

Suffixes: -emia (blood condition), -uria (urine condition), -itis (inflammation), -penia (deficiency), -cytosis (cell increase), -lysis (breakdown), -oma (tumor).

Root examples: cardi- heart, pulmon- lung, ren- kidney, hepat- liver, gastr- stomach, hem/hemat- blood, thromb- clot, myel- marrow.

Reference intervals: serum sodium 135-145 mmol/L; potassium 3.5-5.0 mmol/L; chloride 98-107 mmol/L; total CO2 22-29 mmol/L; glucose fasting 70-99 mg/dL.

Hematology: hemoglobin adult male ~13.5-17.5 g/dL, female ~12.0-15.5 g/dL; hematocrit roughly 3x hemoglobin; MCV 80-100 fL defines normocytic range.

Acid-base: pH 7.35-7.45; respiratory acidosis = low pH with high pCO2; metabolic acidosis = low pH with low HCO3; compensation moves the other parameter in the same direction as the primary disorder's pH shift.

Enzyme markers: troponin I/T for myocardial injury; CK-MB less specific; ALT/AST for hepatocellular injury; ALP and GGT for cholestasis; amylase/lipase for pancreatitis.

Coagulation: PT 11-13.5 s (INR 0.8-1.2), aPTT 25-35 s; PT monitors warfarin (extrinsic pathway), aPTT monitors unfractionated heparin (intrinsic pathway).

Order of draw (CLSI): blood culture, sodium citrate (light blue), serum tube with/without clot activator (red/gold), heparin (green), EDTA (lavender), glycolytic inhibitor (gray).

Additive inversions: light blue 3-4, red/gold 5, green 8, lavender 8, gray 8; never shake; citrate tubes must fill to the marked volume or the 9:1 blood-to-anticoagulant ratio is invalid.

Serum separator tubes must be centrifuged within 2 hours of collection and preferably within 30-60 minutes; delay causes glucose consumption and potassium leakage from cells.

Hemolysis falsely raises potassium, LDH, AST, and hemoglobin; falsely lowers haptoglobin and may interfere with bilirubin and troponin assays.

Tourniquet application should not exceed 1 minute; prolonged stasis raises potassium, protein, and cholesterol and creates hemoconcentration.

24-hour urine collections require refrigeration or chemical preservation during collection; creatinine is measured to verify completeness.

Blood culture sets: collect before antibiotics when possible; adult sets typically 2 sets from separate sites; do not refrigerate routine blood culture bottles, keep at 35-37 C.

Specimen rejection examples: unlabeled or mislabeled container, wrong tube for test, gross hemolysis, clotted anticoagulated sample, expired collection device, insufficient volume for citrate testing.

Beer-Lambert law: absorbance is proportional to concentration times path length times molar absorptivity; linearity fails at high absorbance, so dilution and reanalysis are used.

Immunoassay formats: sandwich (two antibodies, detects large analytes), competitive (labeled antigen competes with patient antigen, used for small haptens), and indirect (detects patient antibody).

Hematology analyzers use impedance (cell counting and volume) and light scatter/flow cytometry (differential); the WBC histogram is flagged when populations overlap.

Blood film review: polychromasia indicates reticulocytosis; schistocytes suggest microangiopathy; spherocytes suggest immune hemolysis or hereditary spherocytosis; target cells suggest liver disease or thalassemia.

Microbiology: Gram stain purple = gram-positive, pink/red = gram-negative; catalase and coagulase differentiate Staphylococcus aureus from other staphylococci.

Urinalysis: reagent strip leukocyte esterase and nitrite screen for UTI; microscopy with >5 WBC/hpf is significant; casts indicate renal origin, not lower tract.

Quality control rules (Westgard): 1-3s rejects, 2-2s rejects, R-4s rejects, 4-1s and 10x reject systematic error; 1-2s is a warning rule.

Delta check compares a current result with the patient's prior result; a difference beyond the established limit triggers specimen or patient verification before reporting.

Patient confidentiality: protected health information may be shared only for treatment, payment, or operations, or as required by law; minimum necessary standard applies.

Breach notification: HIPAA requires notification of affected individuals without unreasonable delay and no later than 60 days after discovery.

Patient identifiers for specimen collection: at least two identifiers, typically full name and date of birth or medical record number; the patient must state them when possible.

Critical result communication: report to the responsible clinician promptly, document read-back, and record the time and names of both parties.

Competency and error disclosure: an error that affects patient care must be reported through the laboratory's incident system and disclosed per institutional policy, not concealed.

Conflicts of interest: gifts or benefits from vendors that could influence purchasing or testing decisions must be disclosed and declined when policy requires.

Cultural and language barriers: use qualified interpreters, avoid family members for consent discussions, and confirm understanding with teach-back.

Social media and photography: no patient-identifiable images or results on personal devices or public platforms; institutional policy governs any permitted use.