Medical Laboratory Scientist flashcards

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

Anion gap formula

Anion gap equals sodium minus the sum of chloride and bicarbonate. A value above the reference range suggests unmeasured anions such as lactate, ketones, or toxins.

Osmolal gap

Measured osmolality minus calculated osmolality. A gap greater than 10 suggests unmeasured osmoles such as methanol, ethylene glycol, or isopropanol.

Friedewald LDL calculation

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

Corrected sodium in hyperglycemia

Add 1.6 mEq/L to measured sodium for every 100 mg/dL glucose above 100. Hyperglycemia dilutes sodium and can mask true hyponatremia.

INR formula

The international normalized ratio equals the patient prothrombin time divided by the mean normal prothrombin time, raised to the ISI power. It standardizes warfarin monitoring.

Mixing study interpretation

Correction of a prolonged aPTT after mixing with normal plasma suggests factor deficiency. Failure to correct suggests an inhibitor such as a lupus anticoagulant or factor antibody.

DIC laboratory pattern

Disseminated intravascular coagulation shows prolonged PT and aPTT, low fibrinogen, elevated D-dimer, thrombocytopenia, and schistocytes. An ISTH score of five or more supports overt DIC.

Direct oral anticoagulant effects

Apixaban and rivaroxaban variably prolong PT, while dabigatran prolongs aPTT. Specific calibrated anti-Xa or dilute thrombin time assays are preferred for quantification.

MCV calculation

Mean corpuscular volume equals hematocrit divided by red cell count in millions per microliter, multiplied by ten. It classifies anemia as microcytic, normocytic, or macrocytic.

Reticulocyte index

The corrected reticulocyte percentage multiplied by the patient hematocrit divided by normal hematocrit, then divided by a maturation factor. It assesses marrow response.

Iron deficiency iron studies

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

CML genetic hallmark

Chronic myeloid leukemia carries the Philadelphia chromosome, t(9;22), producing BCR-ABL1. Peripheral blood shows a left shift with basophilia and thrombocytosis.

Hereditary spherocytosis findings

Hereditary spherocytosis shows spherocytes, elevated MCHC, increased RDW, negative direct antiglobulin test, and splenomegaly. Eosin-5-maleimide binding is a sensitive screening test.

ANA testing limitations

Antinuclear antibody testing is sensitive but not specific for systemic lupus erythematosus. Confirm with anti-dsDNA or anti-Sm, which are more specific, and correlate clinically.

SLE-specific autoantibodies

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

Complement consumption pattern

Low C3 and C4 with low CH50 suggests complement consumption, as in active lupus or infection. Isolated low CH50 suggests terminal complement pathway deficiency.

Type I hypersensitivity

IgE-mediated mast cell degranulation causes immediate reactions such as anaphylaxis. Serum tryptase is elevated during anaphylaxis and specific IgE testing identifies allergens.

ABO reverse grouping

Reverse grouping uses A1 and B reagent red cells to detect patient anti-A and anti-B. Discrepancies with forward typing must be resolved before transfusion.

DAT positive interpretation

A positive direct antiglobulin test with IgG and C3 suggests immune hemolysis. An eluate may identify the antibody coating red cells in autoimmune or delayed hemolytic reactions.

Blood component storage

Red cells are stored at 1-6°C for 35-42 days, platelets at 20-24°C with agitation for 5-7 days, and fresh frozen plasma at -18°C or colder for 12 months.

Emergency release blood

Group O red cells, O-negative for females of childbearing age, and AB or group-specific plasma may be issued before compatibility testing is complete.

Westgard rejection rules

The 1-3s, 2-2s, R-4s, 4-1s, and 10x rules indicate rejection. The 1-2s rule is a warning that prompts inspection of the Levey-Jennings chart.

CLIA test complexity

CLIA categorizes tests as waived, moderate, or high complexity. Non-waived testing requires a qualified laboratory director, documented personnel, and proficiency testing.

Gram stain principle

Gram-positive organisms retain crystal violet due to thick peptidoglycan and stain purple. Gram-negative organisms have thin peptidoglycan and stain pink after safranin counterstain.

Staphylococcus aureus identification

Staphylococcus aureus is catalase positive, coagulase positive, and ferments mannitol. Methicillin resistance is detected by cefoxitin disk or mecA PCR.

Blood culture collection

Collect two sets of aerobic and anaerobic bottles from separate sites before antibiotics. Incubate for five days and perform Gram stain and subculture on positive bottles.

Real-time PCR Ct value

The cycle threshold is the PCR cycle at which fluorescence exceeds background. Lower Ct values generally indicate higher target nucleic acid concentration.

Nucleic acid purity ratios

A260/A280 near 1.8 indicates pure DNA, while near 2.0 indicates pure RNA. A260/A230 assesses contamination by salts and organic solvents.

CLSI order of draw

Blood culture, light blue citrate, serum red or gold, green heparin, lavender EDTA, pink EDTA, then gray fluoride oxalate. Order prevents additive cross-contamination.

Tourniquet time limit

Leave the tourniquet on for no more than one minute. Prolonged application causes hemoconcentration and falsely elevates potassium, proteins, and cell counts.

Acute hemolytic reaction

Suspect acute hemolytic transfusion reaction with fever, chills, flank pain, and hemoglobinuria. Stop the transfusion, maintain IV access, and return the unit to blood bank.