ABPath Combined AP/CP Primary Certification cheat sheet

ABO compatibility: group O packed red cells are universal for red cell transfusion; group AB plasma is universal for plasma because it lacks anti-A and anti-B.

Pretransfusion testing includes ABO/RhD typing, antibody screen, and crossmatch; an electronic crossmatch is permitted only when the antibody screen is negative and validated computer criteria are met.

A positive antibody screen requires antibody identification and antigen-negative donor units for clinically significant antibodies such as anti-K, anti-Jk, anti-Fy, anti-D, and anti-S.

RhD-negative red cells are indicated for RhD-negative females of childbearing potential and for recipients with anti-D; RhD-positive platelets are generally acceptable when no anti-D is present.

Storage: red cells at 1-6 C; platelets at 20-24 C with agitation for up to 5 days; plasma frozen at <= -18 C and used within 24 hours after thawing at 1-6 C.

Acute hemolytic transfusion reaction from ABO incompatibility presents with fever, chills, pain, hemoglobinuria, and hypotension; stop the transfusion immediately and begin compatibility and hemolysis workup.

TRALI occurs within 6 hours with hypoxemia and bilateral infiltrates without volume overload; TACO shows dyspnea, hypertension, elevated BNP, and improvement with diuresis.

For neonatal exchange or intrauterine transfusion, use group O red cells and AB plasma to avoid ABO incompatibility; cytomegalovirus-safe and irradiated products may be indicated.

Anion gap = Na - (Cl + HCO3); reference is approximately 8-12 mmol/L, and add about 2.5 to the gap for each 1 g/dL decrease in albumin below 4 g/dL.

Corrected sodium in hyperglycemia = measured Na + 1.6 mmol/L for every 100 mg/dL glucose above 100 mg/dL; the correction reflects water shift into the extracellular space.

Osmolal gap = measured osmolality - calculated osmolality, where calculated osmolality = 2Na + glucose/18 + BUN/2.8; an elevated gap suggests unmeasured osmoles such as methanol or ethylene glycol.

Hyponatremia evaluation uses serum osmolality first; if hypotonic, check urine osmolality and urine sodium, then assess volume status to distinguish hypovolemic, euvolemic, and hypervolemic causes.

Cardiac troponin diagnosis of myocardial infarction requires a rise and/or fall with at least one value above the 99th percentile upper reference limit plus clinical evidence of ischemia.

Primary hypothyroidism shows elevated TSH with low free T4; subclinical hypothyroidism shows elevated TSH with normal free T4; central hypothyroidism shows low or inappropriately normal TSH with low free T4.

High-titer anti-double-stranded DNA antibodies are relatively specific for systemic lupus erythematosus and correlate with disease activity, especially lupus nephritis; ANA is more sensitive but less specific.

Syphilis reverse algorithm screens with a treponemal immunoassay, then reflexes to RPR or VDRL; discordant results require a second treponemal test, and nontreponemal titers monitor treatment response.

Anemia classification by MCV: microcytic <80 fL, normocytic 80-100 fL, macrocytic >100 fL; RDW reflects red cell size variation and helps distinguish nutritional from thalassemic microcytosis.

Iron deficiency shows low ferritin, low serum iron, high TIBC, and low transferrin saturation; anemia of chronic disease shows normal or high ferritin, low iron, low TIBC, and low saturation.

Hemolysis is supported by elevated LDH, low haptoglobin, elevated indirect bilirubin, reticulocytosis, and increased urine urobilinogen; urine hemosiderin suggests intravascular hemolysis.

A prolonged aPTT that corrects with normal plasma suggests factor deficiency; failure to correct suggests an inhibitor such as a lupus anticoagulant or specific factor inhibitor, sometimes after incubation.

Thrombotic microangiopathy shows schistocytes, thrombocytopenia, elevated LDH, and negative DAT; TTP has severe ADAMTS13 deficiency, while HIT shows anti-PF4 antibodies and thrombosis after heparin exposure.

Chronic myeloid leukemia is defined by t(9;22) producing BCR-ABL1; the fusion tyrosine kinase drives myeloid proliferation and is targeted by tyrosine kinase inhibitors such as imatinib.

Acute promyelocytic leukemia carries t(15;17) producing PML-RARA; it is associated with disseminated intravascular coagulation and is treated with all-trans retinoic acid plus arsenic trioxide or chemotherapy.

Multiple myeloma screening includes serum protein electrophoresis, immunofixation, free light chain assay, and urine protein electrophoresis; diagnosis requires clonal plasma cells plus myeloma-defining events.

Gram stain interprets purple as gram-positive and pink as gram-negative; shape and arrangement guide preliminary identification, such as gram-positive cocci in clusters suggesting Staphylococcus.

Bacterial meningitis CSF typically shows neutrophilic pleocytosis, elevated protein, and low glucose; Gram stain and culture identify the organism, with antigen or molecular tests useful after antibiotics.

MacConkey agar selects gram-negative bacilli and differentiates lactose fermenters, which form pink colonies, from non-lactose fermenters, which remain colorless; bile salts inhibit gram-positive organisms.

Staphylococcus species are catalase-positive gram-positive cocci in clusters; coagulase positivity identifies Staphylococcus aureus, while coagulase-negative staphylococci are common skin flora and device pathogens.

Streptococcus pneumoniae is optochin-susceptible and bile-soluble, whereas viridans group streptococci are optochin-resistant and bile-insoluble; these tests distinguish them in alpha-hemolytic isolates.

Enterobacteriaceae are oxidase-negative, glucose-fermenting gram-negative rods; lactose fermentation on MacConkey is variable, and ESBL production confers resistance to most penicillins and cephalosporins.

Pseudomonas aeruginosa is an oxidase-positive, non-lactose-fermenting gram-negative rod that grows at 42 C, produces pyocyanin, and causes hospital-acquired, burn, and ventilator-associated infections.

Mycobacteria retain carbolfuchsin after acid-alcohol decolorization on Ziehl-Neelsen stain; auramine-rhodamine fluorescence is more sensitive for screening respiratory specimens.

Levey-Jennings charts plot quality control results over time with mean and standard deviation lines; shifts, trends, and outliers signal analytic problems before patient results are reported.

Westgard 1-2s is a warning rule for one control exceeding 2 SD; rejection usually requires 1-3s, 2-2s, R-4s, or 4-1s, depending on the laboratory's validated QC plan.

CLIA categorizes tests as waived, moderate, or high complexity; complexity determines personnel qualifications, quality control, proficiency testing, and the certificate required for testing.

Proficiency testing uses unknown samples compared with peer laboratories; successful participation is required for CLIA certification, and failures trigger corrective action and possible sanctions.

Positive predictive value = true positives / (true positives + false positives); it depends on disease prevalence, so a highly specific test can have low PPV in a low-prevalence population.

Turnaround time should be monitored from order or specimen receipt to result release; delayed subprocesses are identified with time-motion studies and process maps rather than by average alone.

Budget variance = actual cost - expected cost; unfavorable variance may reflect increased test volume, reagent waste, repeat testing, overtime, or contract price changes.

Lean waste categories include defects, overproduction, waiting, non-utilized talent, transportation, inventory, motion, and excess processing; reducing these improves laboratory flow and efficiency.