ASCP C flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ABO reverse grouping

Patient plasma is tested against known A1 and B reagent cells. Expected agglutination confirms the forward type: group A plasma reacts with B cells only, group B with A cells only, group O with both, group AB with neither.

Weak D test

Performed when routine D typing appears negative or weak. Anti-D is incubated at 37°C and antihuman globulin is added; agglutination indicates weak D expression, and donor units testing positive are labeled D-positive.

DAT positive with C3d

The direct antiglobulin test detects antibody or complement coating circulating red cells. C3d-only positivity suggests complement activation, often from cold agglutinins, whereas IgG positivity suggests warm autoimmune hemolysis or recent transfusion.

Platelet storage requirements

Platelets are stored at 20–24°C with continuous gentle agitation for up to 5 days. Cold storage causes shape change and rapid clearance, and platelets carry the highest bacterial contamination risk of any blood component.

Anion gap formula

The anion gap equals sodium minus the sum of chloride and bicarbonate. Reference is roughly 8–16 mmol/L; an elevated gap indicates unmeasured anions such as ketones, lactate, uremic acids, salicylate, or toxic alcohols.

Friedewald LDL calculation

LDL cholesterol equals total cholesterol minus HDL minus triglycerides divided by five, all expressed in mg/dL. The calculation is unreliable when triglycerides exceed 400 mg/dL or in type III dyslipidemia.

Corrected sodium in hyperglycemia

Measured sodium falls about 1.6 mmol/L for every 100 mg/dL glucose above 100 because hypertonic plasma water dilutes it. Corrected Na = measured Na + 1.6 × (glucose − 100)/100.

Beer-Lambert law

Absorbance equals molar absorptivity times path length times concentration. The relationship is linear only over a limited range, so specimens above the analytical range must be diluted and re-assayed for an accurate result.

Mixing study interpretation

Patient plasma is mixed 1:1 with normal plasma and incubated at 37°C. Correction of a prolonged PT or aPTT at one and two hours indicates factor deficiency; failure to correct indicates an inhibitor such as lupus anticoagulant.

MCV with elevated RDW

Microcytic anemia with a high red cell distribution width favors iron deficiency, where red cells are heterogeneous. Thalassemia trait typically shows microcytosis with a normal RDW and a normal or elevated hemoglobin A2.

PT versus aPTT

PT evaluates the extrinsic and common pathway including factor VII and monitors warfarin as the INR. aPTT evaluates the intrinsic and common pathway including factors VIII, IX, XI, and XII and monitors unfractionated heparin.

D-dimer clinical utility

D-dimer is a fibrin degradation product with high sensitivity but low specificity. A negative result helps exclude venous thromboembolism in patients with low or intermediate pretest probability; positive results require imaging confirmation.

Coagulase test

Coagulase converts fibrinogen to fibrin and distinguishes Staphylococcus aureus, which is coagulase positive, from coagulase-negative staphylococci such as S. epidermidis, a frequent blood culture contaminant.

Optochin susceptibility test

An optochin disk placed on a blood agar plate distinguishes Streptococcus pneumoniae, which shows a zone of inhibition, from viridans streptococci. Bile solubility confirms pneumococcus when the disk result is equivocal.

MRSA cefoxitin screen

A cefoxitin disk induces expression of mecA-encoded PBP2a. A zone of 21 mm or less indicates methicillin resistance in Staphylococcus aureus, which is reported resistant to all beta-lactams except ceftaroline.

Oxidase test

The oxidase test detects cytochrome c oxidase activity using an impregnated disk or swab. Positive organisms include Pseudomonas aeruginosa, Neisseria species, and Aeromonas; Enterobacterales such as Escherichia coli are oxidase negative.

IgM versus IgG

IgM is a pentamer and the first antibody produced in a primary response, strongly activates complement, and does not cross the placenta. IgG is a monomer, most abundant, crosses the placenta, and dominates secondary responses.

CH50 assay

CH50 measures the serum dilution needed to lyse 50% of sensitized sheep red cells, assessing classical complement pathway function. Low values suggest complement consumption in immune complex disease or an inherited deficiency.

Anti-dsDNA antibodies

Highly specific for systemic lupus erythematosus and associated with lupus nephritis and disease flares. Serial titers support monitoring, and detection uses Crithidia luciliae immunofluorescence or enzyme immunoassay.

Type I hypersensitivity

IgE bound to mast cells cross-links upon antigen exposure, triggering degranulation and histamine release within minutes. Examples include anaphylaxis, allergic rhinitis, and urticaria; serum tryptase aids diagnosis of anaphylaxis.

Interphase FISH

Fluorescent probes hybridize to specific DNA sequences in non-dividing nuclei, allowing rapid detection of deletions, amplifications, and translocations without cell culture. Common applications include HER2 amplification, BCR-ABL1, and prenatal aneuploidy screening.

BCR-ABL1 fusion

The t(9;22) translocation creates the Philadelphia chromosome and a constitutively active tyrosine kinase. It defines chronic myeloid leukemia, is monitored by quantitative RT-PCR, and is targeted by tyrosine kinase inhibitors.

Real-time PCR Ct value

The cycle threshold is the amplification cycle at which fluorescence crosses a set level. It is inversely proportional to the amount of starting template, so a lower Ct value indicates more target nucleic acid.

Klinefelter syndrome karyotype

47,XXY is the most common male sex chromosome aneuploidy, producing small testes, gynecomastia, tall stature, and infertility with elevated FSH and low testosterone. Diagnosis is confirmed by karyotype or FISH.

Westgard 1-3s rule

A single control measurement exceeding the mean by three standard deviations rejects the analytical run. It is a highly sensitive rule that detects random error and large systematic shifts, usually prompting repeat control testing.

CLIA test complexity categories

The Clinical Laboratory Improvement Amendments classify tests as waived, moderate, or high complexity. Complexity determines personnel qualifications and quality control requirements, and regulated testing requires a certificate of compliance or accreditation.

Proficiency testing

CMS-approved programs distribute unknown specimens that the laboratory tests and reports as it would patient samples. Unsatisfactory performance for a regulated analyte requires corrective action and can jeopardize CLIA certification.

Delta check

An automated rule comparing a current result with the patient's previous value. A change exceeding a defined threshold flags possible specimen mix-up, mislabeling, or a genuine acute clinical change requiring review.

Order of draw

Evacuated tubes are drawn in the order blood culture, light blue citrate, serum red or gold, green heparin, lavender EDTA, then gray fluoride-oxalate. The sequence prevents additive carryover that would alter coagulation and chemistry results.

Citrate tube fill ratio

Light blue tubes contain buffered sodium citrate and require a blood-to-anticoagulant ratio of 9:1. Underfilled tubes contain excess citrate, which falsely prolongs PT and aPTT, so the specimen must be recollected.

EDTA anticoagulant action

Ethylenediaminetetraacetic acid chelates calcium and blocks the coagulation cascade. It preserves blood cell morphology for complete blood counts, but contaminates chemistry specimens with potassium and calcium-chelating effects.

Tourniquet application limit

The tourniquet should be released within one minute of application. Prolonged constriction causes hemoconcentration and falsely elevates potassium, lactate, total protein, and enzyme values by as much as 10 to 20 percent.