MELE flashcards

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

ABO reverse grouping

Uses patient serum with A1 and B reagent cells to detect anti-A and anti-B antibodies; results should match forward grouping. Discrepancies require resolution before transfusion.

Weak D test

Performed when initial anti-D is negative; if positive, label D-positive; if negative, label D-negative. Some policies treat weak D types 1,2,3 as D-negative for transfusion.

Direct antiglobulin test

DAT detects antibody or complement bound to patient red cells in vivo; used in hemolytic disease of newborn, autoimmune hemolysis, and transfusion reactions.

Corrected count increment

CCI = (post - pre platelet count) x body surface area / platelet dose. CCI < 5000 at 1 hour suggests immune platelet refractoriness.

Beer-Lambert law

Absorbance = molar absorptivity x path length x concentration. Absorbance is directly proportional to concentration and path length in spectrophotometry.

Cardiac troponin

Most specific marker of myocardial injury; rises 3-6 hours after onset, peaks 12-24 hours, remains elevated 5-14 days. Used for acute coronary syndrome diagnosis.

Osmolality calculation

Calculated osmolality = 2 x sodium + glucose/18 + BUN/2.8. Measured osmolality uses freezing point depression; gap suggests unmeasured osmoles.

Westgard rules

Quality control rejection rules: 1-3s, 2-2s, R-4s, 4-1s, 10x. 1-2s is a warning. Used with Levey-Jennings charts to detect random and systematic error.

Anemia by MCV

Microcytic anemia: MCV <80 fL (iron deficiency, thalassemia). Normocytic: 80-100 fL (chronic disease). Macrocytic: >100 fL (B12/folate deficiency).

Corrected reticulocyte count

Corrected retic % = retic % x (patient hematocrit / normal hematocrit). Reticulocyte production index further adjusts for maturation time in anemia.

Mixing study

Patient plasma mixed with normal plasma; if aPTT corrects, factor deficiency; if not, inhibitor (e.g., lupus anticoagulant, factor VIII inhibitor).

Hemoglobin electrophoresis

Separates hemoglobins: HbA, HbA2, HbF, HbS, HbC. Sickle cell trait shows HbAS; sickle cell disease shows HbSS. Used to diagnose hemoglobinopathies.

MRSA detection

Cefoxitin disk diffusion or mecA PCR. MRSA is resistant to all beta-lactams; treated with vancomycin or linezolid.

Streptococcus pyogenes

Group A strep; beta-hemolytic, bacitracin sensitive, PYR positive. Causes pharyngitis, rheumatic fever, necrotizing fasciitis.

Pseudomonas aeruginosa

Oxidase positive, non-lactose fermenter, grape-like odor, blue-green pigment. Opportunistic pathogen in burns and cystic fibrosis.

Blood culture collection

Collect 2 sets (aerobic and anaerobic) before antibiotics; incubate 5 days. Each set from a separate venipuncture site.

Antibody structure

IgG monomer, IgM pentamer, IgA dimer. IgG crosses placenta; IgM is first responder in primary immune response. IgA found in secretions.

ELISA

Enzyme-linked immunosorbent assay; enzyme conjugate converts substrate to colored product. Types: direct, indirect, sandwich, competitive. Used for antibody and antigen detection.

Syphilis serology

Non-treponemal tests (RPR, VDRL) for screening; treponemal tests (FTA-ABS, TP-PA) for confirmation. Non-treponemal titers monitor treatment response.

HIV testing algorithm

Fourth-generation antigen/antibody combo is initial test; reactive samples confirmed with HIV-1/HIV-2 antibody differentiation or NAT. Western blot is older confirmatory test.

Urine specific gravity

Reflects urine concentration; dipstick method correlates with osmolality. Normal 1.005-1.030. High in dehydration, SIADH; low in diabetes insipidus.

Urine casts

Hyaline casts normal; RBC casts indicate glomerulonephritis; WBC casts indicate pyelonephritis; granular casts indicate tubular injury.

CSF analysis

Normal: clear, glucose 50-80 mg/dL, protein 15-45 mg/dL, WBC 0-5. Bacterial meningitis: low glucose, high protein, neutrophilic pleocytosis.

Synovial fluid crystals

Gout: needle-shaped, negatively birefringent monosodium urate. Pseudogout: rhomboid, positively birefringent calcium pyrophosphate. Identified by polarized microscopy.

Levey-Jennings chart

Plots quality control values over time with mean and ±2SD limits. Used to detect shifts and trends; interpreted with Westgard rules.

CLIA complexity categories

Waived, moderate, and high complexity. Personnel requirements and quality standards vary by category. Waived tests are simple with low risk of error.

Method validation

Assesses accuracy, precision, analytical sensitivity, specificity, reportable range, and reference intervals before introducing a new test.

Real-time PCR

Uses fluorescent probes to quantify target during amplification. Cycle threshold (Ct) is inversely proportional to initial template amount.

Sanger sequencing

Dideoxy chain termination method; uses labeled ddNTPs to terminate DNA synthesis. Gold standard for single-gene mutation detection.

FISH

Fluorescence in situ hybridization; fluorescent probes bind specific chromosomal sequences. Used for HER2 amplification, aneuploidy, and microdeletions.

Standard precautions

Treat all blood and body fluids as infectious; use gloves, gowns, eye protection. Hand hygiene is the most effective prevention measure.

Chemical safety

Safety Data Sheet (SDS) for each chemical; use fume hood for volatile solvents. Formaldehyde exposure monitored with badges; limit exposure with ventilation.