MELE cheat sheet

ABO reverse grouping uses patient serum and A1 and B reagent cells; forward uses patient cells and anti-A/anti-B. Discrepancies require resolution before release.

Weak D (Du) testing: if initial anti-D is negative at immediate spin, perform weak D test; if positive, label as D-positive; if negative, label as D-negative. Weak D types 1, 2, 3 may be managed as D-negative for transfusion but D-positive for pregnancy in some policies.

Antibody screen: 2-3 cell screen ( heterozygous/ homozygous) at AHG; positive screen requires antibody identification panel. Use LISS or PEG to enhance.

Crossmatch: immediate spin (IS) for ABO compatibility, then AHG crossmatch if antibody screen positive or history of clinically significant antibody.

Clinically significant antibodies: IgG reactive at 37°C or AHG; examples: Rh, Kell, Duffy, Kidd, MNS, Lewis (IgM but can be significant).

Coombs test: direct antiglobulin test (DAT) detects antibody/complement on patient RBCs; indirect (IAT) detects antibody in serum.

Granulocyte serology: HLA and HNA antibodies; use granulocyte agglutination or flow cytometry.

Platelet refractoriness: calculate corrected count increment (CCI) = (post - pre count) x BSA / platelet dose; CCI < 5000 at 1 hour suggests immune refractoriness.

Transfusion reaction workup: clerical check, DAT, visual inspection, culture if sepsis suspected; report to blood bank.

Beer-Lambert law: A = εbc; absorbance directly proportional to concentration and path length.

Enzymatic assays: NADH absorbance at 340 nm; conversion to NAD+ decreases absorbance; measure rate.

Creatinine: Jaffe reaction (alkaline picrate) or enzymatic; eGFR from CKD-EPI equation.

Glucose: hexokinase or glucose oxidase; fasting glucose ≥126 mg/dL on two occasions indicates diabetes.

Cardiac troponin: most specific marker of myocardial injury; rises 3-6 h, peaks 12-24 h, remains elevated 5-14 days.

Electrolytes: sodium by indirect ISE; pseudohyponatremia with hyperlipidemia or hyperproteinemia.

Osmolality: calculated = 2Na + glucose/18 + BUN/2.8; measured by freezing point depression.

Quality control: Levey-Jennings charts; Westgard rules: 1-2s warning, 1-3s, 2-2s, R-4s, 4-1s, 10x rejection.

Complete blood count: RBC, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, WBC with differential, platelet count.

Anemia classification by MCV: microcytic (<80 fL), normocytic (80-100 fL), macrocytic (>100 fL).

Iron studies: iron deficiency shows low ferritin, low serum iron, high TIBC, low saturation; anemia of chronic disease shows low iron, low TIBC, normal/high ferritin.

Reticulocyte count: corrected reticulocyte count = retic % x (patient Hct / normal Hct); reticulocyte production index (RPI) adjusts for maturation.

Hemoglobin electrophoresis: HbA, HbA2, HbF, HbS, HbC; sickle cell trait shows HbAS.

Coagulation: PT/INR monitors warfarin; aPTT monitors unfractionated heparin; mixing study distinguishes factor deficiency (corrects) from inhibitor (does not correct).

Platelet function: bleeding time outdated; use PFA-100 or platelet aggregometry.

Bone marrow: myeloid:erythroid ratio 2:1 to 4:1; assess cellularity by age.

Gram stain: crystal violet, iodine, decolorizer, safranin; Gram-positive purple, Gram-negative pink.

Culture media: blood agar (hemolysis), MacConkey (lactose fermenters pink), chocolate agar (fastidious organisms).

Staphylococcus aureus: catalase positive, coagulase positive, mannitol fermenter; MRSA detected by cefoxitin disk or mecA PCR.

Streptococcus pyogenes: bacitracin sensitive, PYR positive; S. agalactiae: hippurate positive, CAMP positive.

Enterobacteriaceae: oxidase negative, glucose fermenters; lactose fermentation on MacConkey.

Pseudomonas aeruginosa: oxidase positive, non-lactose fermenter, grape-like odor, blue-green pigment.

Antimicrobial susceptibility: disk diffusion (Kirby-Bauer), broth microdilution for MIC; CLSI breakpoints.

Blood culture: collect 2 sets (aerobic and anaerobic) before antibiotics; incubate 5 days.

Mycobacterium tuberculosis: acid-fast stain (Ziehl-Neelsen), Lowenstein-Jensen medium, PCR for rapid detection.

Antibody structure: IgG monomer, IgM pentamer, IgA dimer; IgG crosses placenta.

Primary immune response: IgM first, then IgG; secondary response: rapid IgG.

Complement pathways: classical (IgG/IgM), alternative (microbial surfaces), lectin (mannose).

ELISA: direct, indirect, sandwich, competitive; enzyme conjugate converts substrate to colored product.

Autoimmune markers: ANA (screening), anti-dsDNA (SLE specific), anti-CCP (rheumatoid arthritis), ANCA (vasculitis).

Syphilis serology: non-treponemal (RPR, VDRL) for screening; treponemal (FTA-ABS, TP-PA) for confirmation.

HIV testing: 4th generation antigen/antibody combo; confirm with Western blot or NAT.

Hepatitis B serology: HBsAg (infection), anti-HBs (immunity), anti-HBc IgM (acute).

Urine color: pale yellow (normal), red (blood), brown (bilirubin), cloudy (infection).

Specific gravity: reflects concentrating ability; dipstick method correlates with osmolality.

Dipstick pH: normal 4.5-8.0; alkaline urine with urea-splitting organisms.

Protein: dipstick detects albumin; sulfosalicylic acid test detects all proteins; microalbuminuria.

Glucose: dipstick glucose oxidase; positive in diabetes mellitus or Fanconi syndrome.

Ketones: acetoacetate detected by dipstick; beta-hydroxybutyrate not detected.

Microscopy: RBCs, WBCs, casts (hyaline, granular, RBC, WBC), crystals (calcium oxalate, uric acid).

CSF: normal clear, glucose 50-80 mg/dL, protein 15-45 mg/dL, WBC 0-5; bacterial meningitis shows low glucose, high protein, neutrophilic pleocytosis.

Synovial fluid: normal clear, viscous; gout shows needle-shaped negatively birefringent crystals; pseudogout shows rhomboid positively birefringent.

Quality control: run at least two levels (normal and abnormal) daily; document shifts and trends.

Westgard rules: 1-2s warning, 1-3s, 2-2s, R-4s, 4-1s, 10x rejection.

Levey-Jennings chart: plot control values over time; mean ± 2SD.

Proficiency testing: required by CLIA; failure triggers corrective action.

CLIA categories: waived, moderate, high complexity; personnel requirements vary.

Method validation: accuracy, precision, analytical sensitivity, specificity, reportable range, reference intervals.

Turnaround time (TAT): monitor from order to result; identify bottlenecks.

Document control: policies, procedures, and records must be current and accessible.

PCR: denaturation (94-96°C), annealing (50-65°C), extension (72°C); exponential amplification.

Real-time PCR: fluorescent probes (TaqMan) quantify target; cycle threshold (Ct) inversely proportional to template.

DNA sequencing: Sanger (dideoxy) for single genes; next-generation sequencing (NGS) for panels.

Molecular tests: HIV viral load (RNA), HCV RNA, BCR-ABL1 (quantitative), CFTR mutations.

Southern blot: DNA detection; Northern blot: RNA; Western blot: protein.

FISH: fluorescent probes for chromosomal abnormalities; used in HER2 amplification.

Karyotyping: G-banded chromosomes; detects aneuploidy and large structural changes.

Contamination control: unidirectional workflow, separate pre- and post-amplification areas, UNG.

Standard precautions: treat all blood and body fluids as infectious; use gloves, gowns, eye protection.

Hand hygiene: most effective way to prevent infection; wash with soap and water or alcohol-based rub.

Sharps: do not recap needles; dispose in puncture-resistant containers.

Chemical safety: SDS (Safety Data Sheet) for each chemical; use fume hood for volatile solvents.

Biological spill: absorb, disinfect with 10% bleach or EPA-registered disinfectant, autoclave waste.

Fire safety: PASS (Pull, Aim, Squeeze, Sweep); know location of extinguishers and exits.

Formaldehyde exposure: monitor with badges; limit exposure; use ventilation.

Radiation safety: ALARA (As Low As Reasonably Achievable); dosimeter badges.