ASCP C cheat sheet

ABO: group A cells carry A antigen with anti-B in plasma; group B carries B antigen with anti-A; group O carries neither antigen but both antibodies; group AB carries both antigens and no antibodies.

IgM antibodies (ABO, I, P) agglutinate at immediate spin or room temperature; IgG antibodies (Rh, Kell, Duffy, Kidd) require 37°C incubation and the antiglobulin (AHG) phase.

Weak D testing: when routine D typing appears negative or weak, anti-D is incubated at 37°C followed by AHG; a positive result indicates weak D expression and the unit or patient is reported D-positive.

Immediate-spin crossmatch detects ABO incompatibility; the AHG crossmatch detects clinically significant IgG antibodies directed at donor cells.

Storage limits: red cells 1–6°C for up to 42 days in additive solution; platelets 20–24°C with continuous agitation for 5 days; fresh frozen plasma at or below -18°C for 12 months.

Febrile nonhemolytic reactions are the most common transfusion reaction; acute hemolytic reactions are most often caused by clerical error producing an ABO-incompatible unit.

Hemolytic disease of the newborn: Rh (anti-D) disease is more severe and causes anemia, hydrops, and kernicterus; ABO disease is milder and usually limited to jaundice.

Antibody identification panels use homozygous versus heterozygous cells because dosage effect is strongest with Rh, Kell, Duffy, and Kidd system antibodies.

Beer-Lambert law: absorbance = molar absorptivity × path length × concentration; linearity is limited, so results above the analytical range require dilution and re-assay.

Anion gap = Na − (Cl + HCO3); reference approximately 8–16 mmol/L; an elevated gap indicates unmeasured anions such as ketones, lactate, uremic acids, salicylate, or methanol.

Calculated osmolality = 2[Na] + glucose/18 + BUN/2.8; a measured-minus-calculated difference greater than 10 indicates an unmeasured osmole such as ethanol, methanol, or ethylene glycol.

Friedewald equation: LDL = total cholesterol − HDL − (triglycerides/5) in mg/dL; invalid when triglycerides exceed 400 mg/dL or in type III dyslipidemia.

ALT is more liver-specific than AST; an elevated alkaline phosphatase is attributed to hepatobiliary origin when gamma-glutamyl transferase is also elevated, and to bone when it is not.

Cardiac troponin I and T are the most specific markers of myocardial injury; CK-MB retains value for detecting early reinfarction after an initial event.

Hemoglobin A1c reflects mean glycemia over roughly 2–3 months and is standardized to the NGSP/DCCT reference method.

BUN-to-creatinine ratio above 20:1 suggests prerenal azotemia; a ratio near 10:1 with an elevated creatinine suggests intrinsic renal disease.

Adult reference intervals: hemoglobin 13.5–17.5 g/dL in men and 12.0–15.5 g/dL in women; MCV 80–100 fL; MCHC 32–36 g/dL; platelets 150–450 × 10⁹/L.

Microcytic differential: iron deficiency, thalassemia, anemia of chronic disease, sideroblastic anemia, and lead poisoning; iron deficiency shows low ferritin, high TIBC, and low saturation.

Thalassemia trait shows microcytosis with a normal RDW, target cells, and a normal or elevated hemoglobin A2, distinguishing it from iron deficiency.

PT measures the extrinsic and common pathway (factor VII) and is reported as INR for warfarin; aPTT measures the intrinsic and common pathway (VIII, IX, XI, XII) and monitors unfractionated heparin.

Mixing study: correction of a prolonged PT or aPTT after 1:1 mix with normal plasma indicates factor deficiency; failure to correct at one and two hours indicates an inhibitor such as lupus anticoagulant.

D-dimer has high sensitivity and low specificity; a negative result helps exclude venous thromboembolism in low or intermediate pretest probability patients.

Recurrent cytogenetic associations: t(9;22) BCR-ABL1 in chronic myeloid leukemia and t(15;17) PML-RARA in acute promyelocytic leukemia.

Peripheral smear clues: toxic granulation and Döhle bodies suggest infection or inflammation; basophilic stippling suggests lead poisoning or thalassemia; schistocytes suggest microangiopathy.

Gram-positive cells retain crystal violet through a thick peptidoglycan layer and stain purple; Gram-negative cells decolorize and take up the safranin counterstain, appearing pink.

Staphylococcus aureus is catalase positive, coagulase positive, and ferments mannitol; coagulase-negative staphylococci such as S. epidermidis are common blood culture contaminants.

Streptococcus pyogenes (group A) is bacitracin susceptible and PYR positive; Streptococcus agalactiae (group B) is hippurate positive and CAMP positive.

Streptococcus pneumoniae appears as lancet-shaped diplococci, is optochin susceptible, and is bile soluble; viridans streptococci are optochin resistant.

Enterobacterales ferment glucose and are oxidase negative; Pseudomonas aeruginosa is an oxidase-positive non-fermenter producing pyocyanin and a grape-like odor.

Blood cultures: collect 2–4 sets from separate sites, 20–30 mL per set, before antimicrobial therapy; positive bottles are Gram stained and subcultured without delay.

Methicillin resistance in S. aureus is mediated by mecA-encoding PBP2a and screened with a cefoxitin disk; extended-spectrum beta-lactamases are confirmed by double-disk synergy testing.

Mycobacteria are acid-fast, detected by auramine-rhodamine fluorescence or Ziehl-Neelsen stain, and cultured on Lowenstein-Jensen medium or in liquid MGIT broth.

IgM is a pentamer and the first antibody of a primary response, strongly activates complement, and does not cross the placenta; IgG is a monomer, the most abundant immunoglobulin, and crosses the placenta.

Complement pathways: classical initiated by C1q binding IgG or IgM, alternative driven by microbial surfaces with properdin, and lectin initiated by mannose-binding lectin; CH50 assesses the classical pathway.

Hypersensitivity types: I IgE and mast cells (anaphylaxis), II antibody against cell-bound antigen (hemolysis), III immune complex deposition (serum sickness), IV T-cell mediated and delayed.

Anti-dsDNA and anti-Sm are highly specific for systemic lupus erythematosus; anti-CCP is specific and prognostically useful in rheumatoid arthritis.

ANA patterns: homogeneous suggests anti-dsDNA, speckled suggests extractable nuclear antigens, nucleolar suggests systemic sclerosis, and centromere suggests limited cutaneous scleroderma.

Nephelometry and turbidimetry quantify serum immunoglobulins and complement; serum protein electrophoresis with immunofixation identifies a monoclonal protein and its isotype.

Primary immunodeficiencies: X-linked agammaglobulinemia (BTK mutation, absent B cells), common variable immunodeficiency, DiGeorge syndrome (22q11 deletion, T-cell defect), and SCID.

HLA class I antigens (A, B, C) are expressed on all nucleated cells; class II antigens (DR, DQ, DP) are expressed on antigen-presenting cells and determine transplant matching.

PCR cycle temperatures: denaturation at 94–95°C, primer annealing at roughly 50–65°C, and extension at 72°C, repeated for 30–40 cycles.

In real-time PCR, the cycle threshold is inversely proportional to the amount of starting template; a lower Ct value indicates a higher target concentration.

Sanger sequencing uses dideoxynucleotide chain terminators; next-generation sequencing performs massively parallel sequencing of clonally amplified or single-molecule libraries.

FISH hybridizes fluorescent probes to specific sequences and can be performed on interphase nuclei, so no cell culture or metaphase spread is required.

Karyotyping requires dividing cells arrested in metaphase and resolves approximately 5–10 Mb at a 400–550 band level.

Recurrent translocations: t(9;22) BCR-ABL1 in CML, t(15;17) PML-RARA in APL, t(8;21) RUNX1-RUNX1T1 in AML, and t(14;18) in follicular lymphoma.

Aneuploidy examples: trisomy 21 (Down), trisomy 18 (Edwards), trisomy 13 (Patau), 45,X (Turner), and 47,XXY (Klinefelter).

Trinucleotide repeat disorders: fragile X syndrome from CGG expansion in FMR1 (full mutation above 200 repeats) and Huntington disease from CAG expansion in HTT.

Blotting methods: Southern for DNA, Northern for RNA, and Western for protein; a no-template control must accompany amplification runs to detect contamination.

CLIA '88 classifies tests as waived, moderate, or high complexity; CMS is the oversight agency, and complexity determines personnel qualifications and quality control requirements.

Westgard multirule QC: 1-2s is a warning rule, while 1-3s, 2-2s, R-4s, and 4-1s are rejection rules indicating random or systematic error.

Proficiency testing must be performed for regulated analytes using CMS-approved programs, and proficiency samples must be handled like patient specimens with no interlaboratory communication.

Levey-Jennings charts plot control values over time against the mean and ±1, 2, and 3 standard deviation limits to visualize shifts and trends.

Delta checks compare a current result with the patient's previous value; a change exceeding a defined threshold flags specimen mislabeling, contamination, or true acute change.

Critical values must be reported to the responsible caregiver promptly, with read-back verification and documentation of the time, recipient, and result.

OSHA Bloodborne Pathogens Standard requires a written exposure control plan, hepatitis B vaccination offered to at-risk staff, engineering controls, and personal protective equipment.

Lean and Six Sigma improvement: a six-sigma process yields 3.4 defects per million opportunities; waste reduction targets overproduction, waiting, transport, and defect rework.

Order of draw for evacuated tubes: blood culture bottles, light blue citrate, serum red or gold, green heparin, lavender EDTA, then gray fluoride-oxalate.

EDTA chelates calcium to prevent clotting and is used for complete blood counts because it preserves cell morphology; citrate tubes are used for coagulation testing.

Light blue citrate tubes must be filled to a 9:1 blood-to-anticoagulant ratio; short draws leave excess citrate, falsely prolonging PT and aPTT results.

The tourniquet should be released within one minute; prolonged application causes hemoconcentration and falsely elevates potassium, lactate, total protein, and enzyme values.

Needle selection: 21 gauge is standard for routine venipuncture; 23–25 gauge butterfly sets are used for fragile, small, or sclerosed veins.

Infant heel puncture is made on the medial or lateral plantar surface; the central arch and previously punctured sites are avoided to prevent bone or nerve injury.

Blood cultures require two sets from separate sites totaling 20–30 mL and should be drawn before antimicrobial administration whenever possible.

Specimen rejection criteria include unlabeled or mislabeled tubes, incorrect tube type for the test, clotted anticoagulated samples, gross hemolysis, and insufficient volume.

Protect bilirubin specimens from light and transport ammonia, lactate, blood gas, and ACTH samples on ice to prevent preanalytical change.