ASCP PBT cheat sheet

Order of draw (CLSI): blood culture, light blue (citrate), serum tube (red/gold), heparin (green), EDTA (lavender), oxalate/fluoride (gray).

Light blue citrate tube must be filled to the indicated volume; short draws raise the citrate-to-blood ratio and falsely prolong PT/aPTT.

Tourniquet should be released within 1 minute; prolonged application causes hemoconcentration and falsely elevated potassium, protein, and cell counts.

Preferred venipuncture site is the antecubital fossa (median cubital, cephalic, basilic veins); avoid the arm with IV fluid, mastectomy, or fistula.

Hemolysis falsely elevates potassium, LDH, AST, and phosphate and falsely lowers glucose and bilirubin.

Serum separator tubes must clot 10-30 minutes before centrifugation; EDTA tubes are inverted 8-10 times, citrate 3-4 times.

Ethylene glycol and methanol poisoning are monitored with osmolal gap; draw in a tube without gel for volatile testing.

Capillary puncture: wipe away the first drop, avoid squeezing (tissue fluid dilution), and warm the site to increase blood flow.

Blood culture sets: collect before antibiotics, 20-30 mL per set from adults, inoculate aerobic bottle first.

ABO: A antigen with anti-B, B with anti-A, AB with none, O with anti-A and anti-B; reverse grouping confirms.

Rh(D) negative patients must receive D-negative red cells; anti-D is IgG and causes hemolytic disease of the newborn.

Antibody screen uses indirect antiglobulin test (IAT) with anti-IgG; positive screen requires an antibody identification panel.

Positive autocontrol suggests autoantibody or warm/cold autoagglutinin; allogeneic antibody suggests prior sensitization.

Crossmatch: immediate spin detects ABO incompatibility; AHG phase detects clinically significant IgG antibodies.

Anti-A1 lectin (Dolichos biflorus) distinguishes A1 from A2; A2 cells may have anti-A1 in serum.

Weak D testing is performed on apparent D-negative donors; patients typed weak D are managed as D-positive for transfusion.

Coombs test: direct (DAT) detects antibody/complement on patient RBCs; indirect detects antibody in serum.

Granulocyte and platelet transfusions are ABO-compatible where possible; plasma must be ABO-compatible with recipient RBCs.

Sodium is the major extracellular cation; hyponatremia is evaluated with serum osmolality and volume status.

Anion gap = Na − (Cl + HCO3); normal 8-12 mEq/L; elevated gap suggests ketoacidosis, lactic acidosis, or toxins.

Corrected calcium = measured Ca + 0.8 × (4.0 − albumin); ionized calcium is the physiologically active fraction.

Estimated GFR uses creatinine with CKD-EPI; creatinine rises only after substantial loss of renal function.

Enzymes: ALT more liver-specific than AST; ALP rises with biliary obstruction; CK-MB and troponin indicate myocardial injury.

Glucose measurement: fluoride tube inhibits glycolysis; fasting glucose ≥126 mg/dL or HbA1c ≥6.5% supports diabetes.

Troponin is the preferred cardiac marker; rises 3-6 hours after injury and remains elevated for days.

Bilirubin: unconjugated is indirect (hemolysis), conjugated is direct (cholestasis); delta bilirubin is albumin-bound.

Lipemia, hemolysis, and icterus interfere with spectrophotometric assays; report as H, L, or I indices.

PT measures extrinsic and common pathway (factors VII, X, V, II, fibrinogen); reported as INR for warfarin monitoring.

aPTT measures intrinsic and common pathway (VIII, IX, XI, XII, X, V, II, fibrinogen); used for heparin monitoring.

Thrombin time and fibrinogen are prolonged by heparin, direct thrombin inhibitors, and dysfibrinogenemia.

Mixing study: correction of prolonged PT/aPTT indicates factor deficiency; failure to correct suggests inhibitor.

D-dimer is a fibrin degradation product; elevated in DVT, PE, DIC, and inflammation; high negative predictive value.

Platelet count <50,000/µL may cause bleeding; <20,000/µL is a risk for spontaneous hemorrhage.

Heparin therapy: monitor aPTT or anti-Xa; protamine sulfate reverses unfractionated heparin.

Warfarin inhibits vitamin K-dependent factors II, VII, IX, X; INR target usually 2-3.

Blood for coagulation testing should be drawn into 3.2% sodium citrate; fill to line and test within 4 hours.

Reference intervals: hemoglobin 13.5-17.5 g/dL (men), 12.0-15.5 g/dL (women); hematocrit roughly 3× hemoglobin.

MCV classifies anemia: microcytic (<80 fL), normocytic (80-100 fL), macrocytic (>100 fL).

Reticulocyte count reflects marrow response; corrected retic = retic % × (patient Hct / normal Hct).

Iron deficiency: low ferritin, low serum iron, high TIBC, low saturation; anemia of chronic disease shows high ferritin, low TIBC.

Megaloblastic anemia (B12/folate) shows macrocytes, hypersegmented neutrophils, and elevated LDH.

Sickle cell: HbS on hemoglobin electrophoresis; peripheral smear shows sickle cells and target cells.

Leukocyte differential: neutrophils 50-70%, lymphocytes 20-40%, monocytes 2-8%, eosinophils 1-4%, basophils 0-1%.

Platelets 150,000-450,000/µL; thrombocytopenia confirmed by smear to exclude clumping.

ESR is affected by anemia, age, and inflammation; not diagnostic alone.

Primary immune response: IgM first, then IgG; secondary response is predominantly IgG with higher affinity.

Complement: classical pathway activated by IgG/IgM-antigen complexes; alternative by microbial surfaces.

ELISA formats: sandwich detects antigen, indirect detects antibody; false positives from rheumatoid factor and heterophile antibodies.

ANA is a screening test for connective tissue disease; positive results require titer and pattern interpretation.

Anti-dsDNA and anti-Sm are specific for SLE; anti-histone suggests drug-induced lupus.

Rheumatoid factor is an IgM antibody against IgG Fc; positive in RA and other chronic inflammatory states.

Flow cytometry identifies cell populations by surface markers (CD4 T cells, CD19 B cells, CD34 stem cells).

HIV screening uses combination antigen/antibody immunoassay; reactive results require confirmatory differentiation assay.

Immunofixation identifies monoclonal proteins (M-spike) in multiple myeloma and MGUS.

CLIA '88 classifies tests as waived, moderate, or high complexity; waived tests require a certificate of waiver.

Proficiency testing (PT) is required for regulated analytes; failure can lead to sanctions.

Quality control: run two levels daily for most analytes; Westgard rules detect random and systematic error.

Levey-Jennings charts plot QC values over time; 1-2s warning, 1-3s and 2-2s rejection rules.

Delta check compares current result with prior patient result to detect specimen mix-up or error.

Turnaround time (TAT) is measured from order to result reporting; monitored as a quality indicator.

CAP and Joint Commission accredit laboratories; CAP inspections emphasize quality management.

Specimen rejection criteria include unlabeled tubes, hemolysis, insufficient volume, and wrong tube type.

Cost accounting: direct costs include reagents and labor; indirect costs include overhead and utilities.

Gram stain: gram-positive purple, gram-negative pink; morphology (cocci, bacilli) guides preliminary identification.

Blood culture bottles: aerobic and anaerobic; incubate at 35°C and monitor for 5 days.

Urine culture: colony count ≥100,000 CFU/mL suggests infection; mixed flora suggests contamination.

Staphylococcus aureus: catalase positive, coagulase positive; MRSA detected by cefoxitin disk or PCR.

Streptococcus pyogenes: beta-hemolytic, bacitracin sensitive; causes pharyngitis and post-streptococcal sequelae.

Enterobacteriaceae are lactose-fermenting gram-negative rods; E. coli is indole positive and oxidase negative.

Pseudomonas aeruginosa: oxidase positive, non-lactose fermenting, grape-like odor, blue-green pigment.

Acid-fast stain (Ziehl-Neelsen) detects mycobacteria; culture requires weeks on Lowenstein-Jensen medium.

Antimicrobial susceptibility: disk diffusion (Kirby-Bauer) and MIC methods; report as S, I, or R.