ASCP PBT flashcards

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

Order of draw

Sequence for venipuncture collection: blood culture, citrate, serum, heparin, EDTA, fluoride. Following the order prevents additive carryover that can alter coagulation and chemistry results.

Hemolysis effect

Rupture of red cells releases potassium, LDH, and AST into serum, falsely elevating them, while diluting glucose and bilirubin. Specimens with visible hemolysis are often rejected for chemistry testing.

Citrate tube fill

Light blue tubes must be filled to the marked volume because underfilling increases the citrate-to-blood ratio, falsely prolonging PT and aPTT. Discard tubes are used before coagulation draws.

Tourniquet time limit

Tourniquet application should not exceed one minute. Prolonged constriction causes hemoconcentration, falsely raising potassium, total protein, and cell counts.

Capillary puncture first drop

The first drop of capillary blood is wiped away because it may contain tissue fluid and alcohol. Squeezing the site is avoided to prevent hemolysis and dilution.

ABO reverse grouping

Serum is tested against known A and B cells to detect anti-A and anti-B. Reverse grouping confirms forward typing and detects discrepancies from missing antibodies or unexpected antibodies.

Direct antiglobulin test

DAT detects antibody or complement bound to patient red cells using anti-human globulin. It is used to investigate hemolytic transfusion reactions and hemolytic disease of the newborn.

Indirect antiglobulin test

IAT detects antibodies in serum that bind reagent red cells, then are detected with anti-IgG. Antibody screens and crossmatches use this method.

Weak D testing

Weak D testing determines whether a D-negative-appearing donor expresses a weak D antigen. Donors testing weak D positive are labeled D-positive to prevent anti-D immunization in recipients.

Anion gap formula

Anion gap equals sodium minus the sum of chloride and bicarbonate, normally 8 to 12 mEq/L. An elevated gap suggests ketoacidosis, lactic acidosis, or toxin ingestion.

Corrected calcium

Corrected calcium equals measured calcium plus 0.8 times (4.0 minus albumin). It estimates calcium status when albumin is abnormal because calcium binds albumin.

Troponin

Troponin is the preferred marker of myocardial injury, rising 3 to 6 hours after damage and remaining elevated for days. It is more cardiac-specific than CK-MB.

Direct versus indirect bilirubin

Direct bilirubin is conjugated and elevated in cholestasis, while indirect is unconjugated and elevated in hemolysis. Delta bilirubin is bound to albumin and persists after resolution.

Creatinine and GFR

Creatinine is used with CKD-EPI to estimate glomerular filtration rate. Creatinine rises only after substantial renal function is lost, so early injury may be missed.

PT and INR

Prothrombin time measures the extrinsic and common pathways and is reported as INR for warfarin monitoring. INR target is usually 2 to 3 for most indications.

aPTT use

Activated partial thromboplastin time measures the intrinsic and common pathways. It is used to monitor unfractionated heparin therapy and detect factor deficiencies.

Mixing study

Patient plasma is mixed with normal plasma to distinguish factor deficiency from inhibitor. Correction indicates deficiency; failure to correct suggests an inhibitor such as lupus anticoagulant.

D-dimer

D-dimer is a fibrin degradation product elevated in thrombosis, DIC, and inflammation. Its high negative predictive value helps exclude pulmonary embolism and deep vein thrombosis.

MCV anemia classification

Mean corpuscular volume classifies anemia as microcytic below 80 fL, normocytic 80 to 100 fL, and macrocytic above 100 fL. This guides the differential diagnosis.

Corrected reticulocyte count

Corrected reticulocyte count equals reticulocyte percent times patient hematocrit divided by normal hematocrit. It assesses whether marrow response is appropriate for the degree of anemia.

Iron deficiency indices

Iron deficiency shows low ferritin, low serum iron, high TIBC, and low transferrin saturation. Anemia of chronic disease shows high ferritin and low TIBC.

Megaloblastic anemia findings

Vitamin B12 or folate deficiency produces macrocytes, hypersegmented neutrophils, and elevated LDH. B12 deficiency may also cause neurologic symptoms.

Primary versus secondary response

The primary immune response produces IgM first, then IgG. The secondary response is faster and predominantly IgG with higher antibody affinity.

Complement classical pathway

The classical complement pathway is activated by antigen-antibody complexes containing IgG or IgM. The alternative pathway is activated directly by microbial surfaces.

ELISA formats

Sandwich ELISA detects antigen using two antibodies, while indirect ELISA detects patient antibody. Rheumatoid factor and heterophile antibodies can cause false-positive results.

SLE-specific antibodies

Anti-double-stranded DNA and anti-Sm are highly specific for systemic lupus erythematosus. Anti-histone antibodies suggest drug-induced lupus.

CLIA test complexity

CLIA classifies tests as waived, moderate, or high complexity. Waived testing requires a certificate of waiver and minimal oversight.

Westgard rules

Westgard rules interpret quality control charts: 1-2s is a warning, while 1-3s and 2-2s indicate rejection. They detect random and systematic analytical error.

Delta check

A delta check compares a current result with the patient's prior result. Large differences flag possible specimen mix-up, transcription error, or acute clinical change.

Gram stain interpretation

Gram-positive organisms stain purple and gram-negative pink. Morphology, such as cocci in clusters, provides preliminary identification before culture results.

Staphylococcus aureus tests

Staphylococcus aureus is catalase positive and coagulase positive. Methicillin resistance is detected with cefoxitin disk testing or molecular methods.

Pseudomonas aeruginosa features

Pseudomonas aeruginosa is an oxidase-positive, non-lactose-fermenting gram-negative rod. It produces blue-green pigment and a grape-like odor.