MLT flashcards
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- Universal red cell donor
- Group O negative red cells lack A, B, and D antigens, so they can be transfused to most recipients before compatibility testing is complete.
- Acute hemolytic transfusion reaction
- Most often caused by ABO incompatibility from clerical error; fever, chills, flank pain, hypotension, and hemoglobinuria appear shortly after transfusion starts.
- Direct antiglobulin test
- DAT uses anti-human globulin to detect IgG or complement bound to red cells in vivo, helping diagnose autoimmune hemolysis and delayed transfusion reactions.
- FFP storage temperature
- Fresh frozen plasma must be stored at -18 C or colder and remains usable for about 12 months; once thawed it is stored at 1-6 C.
- Rh immune globulin
- Anti-D given to D-negative mothers prevents alloimmunization to fetal D-positive red cells; it is indicated during pregnancy and after delivery of a D-positive infant.
- Beer-Lambert law
- Absorbance equals molar absorptivity times path length times concentration, so absorbance is directly proportional to analyte concentration in a fixed cuvette.
- Anion gap formula
- Anion gap equals sodium minus the sum of chloride and bicarbonate; the reference range is about 8 to 12 mmol/L when potassium is excluded.
- Hemoglobin A1c
- HbA1c reflects average blood glucose over roughly two to three months by measuring nonenzymatic glycation of hemoglobin; it is used to monitor diabetes.
- Friedewald LDL calculation
- LDL cholesterol equals total cholesterol minus HDL cholesterol minus triglycerides divided by five; the formula is unreliable when triglycerides exceed 400 mg/dL.
- Jaffe creatinine method
- Creatinine reacts with alkaline picrate to form a colored complex measured photometrically; the method is nonspecific and can be affected by glucose and ketones.
- Mean corpuscular volume
- MCV equals hematocrit divided by red cell count times ten, reported in femtoliters; it classifies anemia as microcytic, normocytic, or macrocytic.
- Corrected reticulocyte count
- Reticulocyte percentage multiplied by the patient hematocrit divided by a normal hematocrit adjusts for anemia severity when assessing marrow response.
- International normalized ratio
- INR standardizes prothrombin time using the thromboplastin ISI and is used to monitor warfarin therapy, with typical target ranges of 2 to 3.
- Iron deficiency profile
- Iron deficiency anemia shows low ferritin, low serum iron, high total iron-binding capacity, and microcytic hypochromic red cells with elevated RDW.
- Sickle cell screening
- Solubility testing detects hemoglobin S, while hemoglobin electrophoresis or high-performance liquid chromatography confirms the specific hemoglobin variant and distinguishes trait from disease.
- Gram stain decolorizer
- Alcohol-acetone removes crystal violet from gram-negative cells but not gram-positive cells; gram-positive organisms remain purple and gram-negative organisms take the safranin counterstain.
- Catalase and coagulase
- Catalase distinguishes staphylococci from streptococci; coagulase positivity identifies Staphylococcus aureus among catalase-positive gram-positive cocci.
- MacConkey agar lactose
- Lactose-fermenting gram-negative bacilli produce pink colonies on MacConkey agar, while non-lactose fermenters remain colorless or pale.
- Blood culture collection
- Draw two or more sets from separate sites, usually 20 to 30 mL total for adults, before antibiotics; incubate routinely for five days.
- Ziehl-Neelsen stain
- Acid-fast staining uses carbolfuchsin with heat or phenol; mycobacteria retain the red stain after acid-alcohol decolorization and appear as red bacilli.
- Urine specific gravity
- Specific gravity reflects urine solute concentration, normally about 1.005 to 1.030; it is measured by refractometry or reagent strip and rises with dehydration.
- Leukocyte esterase
- Reagent strip leukocyte esterase detects neutrophil esterases as an indirect marker of pyuria and is used with nitrite to screen for urinary tract infection.
- Red blood cell cast
- RBC casts form in renal tubules and indicate glomerular bleeding, most classically glomerulonephritis; they appear as cylindrical molds containing red cells.
- CSF glucose reference
- Normal cerebrospinal fluid glucose is about 60 percent of the simultaneous serum glucose, typically 40 to 70 mg/dL; low values suggest bacterial meningitis.
- Primary immune response
- Initial exposure produces mostly IgM antibody after a lag of several days; the response is slower and lower in titer than a subsequent exposure.
- IgG placental transfer
- IgG is the only immunoglobulin that crosses the placenta efficiently, providing passive maternal immunity to the fetus and causing hemolytic disease of the newborn.
- Sandwich ELISA
- A capture antibody binds antigen, a second enzyme-labeled antibody detects it, and substrate conversion produces color proportional to antigen concentration.
- Rheumatoid factor
- Rheumatoid factor is usually IgM antibody directed against the Fc portion of IgG; it is common in rheumatoid arthritis but not specific for it.
- Westgard 1-3s rule
- A single quality control result exceeding the mean by three standard deviations is rejected; this rule detects random error and is often used with other rules.
- Coefficient of variation
- CV equals the standard deviation divided by the mean times 100, expressing assay imprecision as a percentage independent of measurement units.
- Proficiency testing
- External proficiency testing sends unknown specimens to laboratories; results are compared with peer groups and unacceptable performance requires corrective action under CLIA.
- Delta check
- A delta check compares a current result with the patient's previous value and flags a change exceeding a defined limit for investigation before reporting.