ABPath Clinical Pathology flashcards
ABPath Clinical Pathology · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Anion gap formula
- Anion gap = (Na+) − (Cl− + HCO3−). Reference is approximately 8–12 mmol/L. An elevated gap suggests unmeasured anions such as ketones, lactate, or toxins.
- Corrected calcium formula
- Corrected calcium (mg/dL) = measured calcium + 0.8 × (4.0 − albumin in g/dL). Ionized calcium is the physiologically active fraction and is not affected by albumin.
- Serum osmolal gap
- Osmolal gap = measured osmolality − calculated osmolality (2[Na+] + glucose/18 + BUN/2.8). A gap greater than 10 mOsm/kg suggests unmeasured osmoles such as methanol or ethylene glycol.
- Friedewald LDL calculation
- LDL = total cholesterol − HDL − triglycerides/5, all in mg/dL. This estimate is valid only when triglycerides are below 400 mg/dL; above that, use direct measurement.
- Troponin in acute MI
- Cardiac troponin I or T is the preferred marker of myocardial necrosis. Acute myocardial injury requires a rise and fall with at least one value above the 99th percentile upper reference limit.
- High anion gap acidosis causes
- Causes include ketoacidosis, lactic acidosis, renal failure, and toxins such as salicylate, methanol, ethylene glycol, and propylene glycol. Non-gap acidosis reflects bicarbonate loss or renal tubular acidosis.
- MCV calculation
- MCV in femtoliters = (hematocrit ÷ red cell count) × 10. It classifies anemia as microcytic, normocytic, or macrocytic and guides the initial diagnostic workup.
- Corrected reticulocyte index
- Reticulocyte index = retic percent × (patient hematocrit ÷ normal hematocrit) ÷ maturation correction. An elevated index indicates a regenerative marrow response; a low index indicates hypoproduction.
- Iron deficiency laboratory pattern
- Iron deficiency shows low ferritin, low serum iron, high total iron-binding capacity, and low transferrin saturation. Anemia of chronic disease shows low iron and TIBC with normal or high ferritin.
- Coagulation pathway factors
- Intrinsic pathway uses factors VIII, IX, XI, and XII; extrinsic uses factor VII; common pathway uses I, II, V, and X. PT screens extrinsic and common; aPTT screens intrinsic and common.
- Mixing study interpretation
- Correction of a prolonged PT or aPTT after mixing with normal plasma indicates factor deficiency. Failure to correct indicates an inhibitor such as a lupus anticoagulant or factor VIII inhibitor.
- Disseminated intravascular coagulation
- DIC shows prolonged PT and aPTT, low fibrinogen, elevated D-dimer and fibrin degradation products, thrombocytopenia, and schistocytes. It reflects consumptive coagulopathy from sepsis, malignancy, or obstetric complications.
- APL translocation
- Acute promyelocytic leukemia carries t(15;17) forming PML-RARA. It is associated with Auer rods, disseminated intravascular coagulation, and response to all-trans retinoic acid.
- Gram stain morphology rules
- Gram-positive cocci in clusters suggest Staphylococcus; in chains suggest Streptococcus; in pairs suggest pneumococcus or Enterococcus. Gram-negative rods are classified further by lactose fermentation and oxidase testing.
- Streptococcus pneumoniae identification
- Pneumococci are alpha-hemolytic, optochin-sensitive, and bile-soluble. Viridans streptococci are also alpha-hemolytic but are optochin-resistant and not bile-soluble.
- Lancefield group A and B
- Group A Streptococcus pyogenes is bacitracin-sensitive. Group B Streptococcus agalactiae is hippurate-positive and CAMP-positive. Both are beta-hemolytic and cause distinct clinical syndromes.
- MacConkey lactose reaction
- Lactose-fermenting Gram-negative rods appear pink on MacConkey agar. Non-lactose fermenters such as Pseudomonas, Salmonella, and Shigella appear colorless, helping guide organism identification.
- Oxidase-positive Gram-negative rods
- Oxidase-positive organisms include Pseudomonas, Neisseria, Vibrio, and Aeromonas. Enterobacterales are oxidase-negative, so oxidase testing helps separate these groups.
- MRSA detection methods
- MRSA is detected with a cefoxitin disk or by testing for mecA or PBP2a. Cefoxitin is a better inducer than oxacillin for detecting methicillin resistance in staphylococci.
- ABO blood group antigens
- Type A has A antigen and anti-B; type B has B antigen and anti-A; type AB has both antigens and no antibodies; type O has neither antigen and both anti-A and anti-B.
- Indirect antiglobulin test
- The indirect antiglobulin test detects unexpected red cell antibodies in patient serum. A positive screen requires antibody identification and selection of antigen-negative units for transfusion.
- Direct antiglobulin test
- The direct antiglobulin test detects antibody or complement bound to red cells. It is positive in autoimmune hemolytic anemia, hemolytic disease of the newborn, and drug-induced hemolysis.
- Delayed hemolytic reaction
- A delayed hemolytic transfusion reaction occurs 3–14 days after transfusion with falling hemoglobin, positive DAT, and a newly appearing alloantibody. It is usually caused by an anamnestic response.
- ANCA patterns
- c-ANCA targets proteinase 3 and is associated with granulomatosis with polyangiitis. p-ANCA targets myeloperoxidase and is associated with microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis.
- Karyotype versus FISH
- Karyotyping resolves structural changes at about 5–10 Mb and detects balanced rearrangements. FISH targets specific loci at roughly 100–200 kb but only detects the sequences probed.
- t(9;22) BCR-ABL1
- The Philadelphia chromosome t(9;22)(q34;q11.2) fuses BCR to ABL1. It defines chronic myeloid leukemia and occurs in a subset of acute lymphoblastic leukemias.
- JAK2 V617F mutation
- JAK2 V617F is present in most polycythemia vera and about half of essential thrombocythemia and primary myelofibrosis. JAK2-negative cases may have CALR or MPL mutations.
- HER2 FISH interpretation
- HER2 amplification is present when the HER2/CEP17 ratio is at least 2.0 or the average HER2 copy number is at least 6 signals per cell. Results guide trastuzumab eligibility.
- Analytic sensitivity formula
- Sensitivity = true positives ÷ (true positives + false negatives). Specificity = true negatives ÷ (true negatives + false positives). Positive predictive value depends on disease prevalence.
- Six Sigma metric
- Six Sigma = (total allowable error − |bias|) ÷ coefficient of variation. Higher values mean fewer defects; values of 6 or more are considered world-class and below 3 unacceptable.
- Westgard 1-3s rule
- The 1-3s rule rejects a run when a single control result exceeds the mean by more than 3 standard deviations. It is a warning rule often used to trigger inspection of other rules.
- Westgard 2-2s rule
- The 2-2s rule rejects a run when two consecutive control results exceed 2 standard deviations on the same side of the mean. It detects systematic error such as a shift or calibration bias.