ASCP MLA flashcards

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

Order of draw

CLSI venipuncture sequence: blood culture, light-blue citrate, red or gold serum, green heparin, lavender EDTA, gray fluoride-oxalate; the order prevents additive carryover that would distort later tubes.

Citrate tube fill ratio

Light-blue 3.2% sodium citrate tubes require a 9:1 blood-to-anticoagulant ratio; underfilled tubes contain excess citrate and yield falsely prolonged PT and aPTT results.

Hemolysis analyte effects

Hemolysis falsely raises serum potassium, LDH, AST, and phosphate, and adds free hemoglobin that interferes with photometric assays; grossly hemolyzed specimens are rejected for those tests.

Cold agglutinin handling

Clot and transport the specimen at 37°C and separate the serum warm; otherwise cold-reacting IgM agglutinins bind red cells and falsely lower the RBC count while raising MCV.

Fluoride oxalate tube

Gray-top tubes contain sodium fluoride, which inhibits glycolysis, plus potassium oxalate; plasma glucose remains stable about 24 hours when cells cannot be separated promptly.

Tourniquet time artifact

Tourniquet application longer than one minute causes hemoconcentration, falsely elevating potassium, total protein, and lipid concentrations; release the tourniquet and recollect.

24-hour urine collection

Discard the first morning void, then collect every void through the same time the next day, refrigerate or add preservative, record the total volume, and mix well before aliquoting.

Rule of three

In normocytic anemia, hemoglobin in g/dL multiplied by three approximates hematocrit in percent; a large discrepancy suggests an index error or abnormal red cell morphology.

MCV calculation

MCV in femtoliters equals hematocrit percent times ten, divided by the RBC count in millions per microliter; it classifies anemia as microcytic, normocytic, or macrocytic.

Mentzer index

MCV divided by the RBC count in millions per microliter; a value below 13 favors thalassemia trait, while a value above 13 favors iron deficiency anemia.

Mixing study result

A prolonged aPTT that corrects when mixed with normal plasma indicates a factor deficiency; failure to correct after incubation indicates an inhibitor such as lupus anticoagulant.

Corrected reticulocyte count

Reticulocyte percent multiplied by the patient hematocrit and divided by a normal hematocrit of 45%; a maturation factor correction is applied when anemia is present.

INR formula

INR equals the patient prothrombin time divided by the mean normal PT, raised to the ISI power of the thromboplastin reagent; it standardizes warfarin monitoring across laboratories.

Platelet smear estimate

One platelet per oil-immersion field corresponds to roughly 10,000 to 20,000 platelets per microliter; eight to twenty per field spans the normal range.

Anion gap

Sodium minus the sum of chloride and bicarbonate, normally 8 to 12 mmol/L; add 2.5 mmol/L for every 1 g/dL that albumin falls below 4.0.

Corrected calcium

Measured total calcium plus 0.8 times (4.0 minus the serum albumin in g/dL); it estimates the calcium concentration adjusted for hypoalbuminemia.

Friedewald LDL

LDL cholesterol equals total cholesterol minus HDL cholesterol minus triglycerides divided by five; the calculation is invalid when triglycerides exceed 400 mg/dL.

Cockcroft-Gault clearance

Creatinine clearance in mL/min equals (140 minus age) times weight in kg, divided by 72 times serum creatinine, then multiplied by 0.85 for females.

Osmolal gap

Measured osmolality minus calculated osmolality (2 Na plus glucose/18 plus BUN/2.8); a gap above 10 suggests unmeasured osmoles such as methanol or ethylene glycol.

Troponin 99th percentile

Cardiac troponin I or T exceeding the assay's 99th percentile upper reference limit, together with a rising or falling pattern, defines acute myocardial injury.

MacConkey agar

Selective and differential medium containing bile salts and crystal violet; lactose fermenters such as Escherichia coli form pink colonies, while non-fermenters remain colorless.

Optochin disk

A 6-mm optochin disk producing an inhibition zone of 14 mm or more identifies Streptococcus pneumoniae, which is also soluble in bile.

Coagulase test

Coagulase converts fibrinogen to fibrin; a positive slide or tube test separates Staphylococcus aureus from coagulase-negative staphylococci.

Significant bacteriuria

In a clean-catch urine, 100,000 colony-forming units per mL of a single organism indicates infection; lower counts can be significant with symptoms or catheter collection.

Kirby-Bauer diffusion

Antibiotic disks diffuse into inoculated Mueller-Hinton agar; zone diameters are compared with CLSI tables and reported as susceptible, intermediate, or resistant.

India ink preparation

Negative staining of cerebrospinal fluid shows an encapsulated yeast surrounded by a clear halo, a finding consistent with Cryptococcus neoformans.

1-3s rule

One control result exceeds the mean by three standard deviations; the analytical run is rejected because the deviation indicates random error.

2-2s rule

Two consecutive control values exceed the same plus or minus two standard deviation limit; the run is rejected, usually because of systematic error.

Coefficient of variation

CV equals the standard deviation divided by the mean, multiplied by 100; it expresses assay imprecision as a percentage so methods can be compared.

Sensitivity and specificity

Sensitivity is true positives divided by all patients with disease; specificity is true negatives divided by all patients without disease, and both are intrinsic test properties.

CLIA complexity categories

Tests are classified as waived, moderate, or high complexity; a laboratory holding a certificate of waiver may perform only waived testing.

Delta check

A delta check compares a patient's current result with the previous value; an excessive change flags possible specimen mix-up or mislabeling for investigation.