NMCB Licensure Exam cheat sheet

pH = -log[H+]; each unit of pH change represents a tenfold change in hydrogen ion concentration, and pH 7.4 corresponds to [H+] ≈ 40 nmol/L.

Beer-Lambert law: A = εbc, so absorbance is directly proportional to concentration and path length; deviations occur at high absorbance (>2.0) or with polychromatic light.

Osmolality (mOsm/kg) ≈ 2[Na+] + [glucose]/18 + [BUN]/2.8, using mg/dL units for glucose and urea nitrogen.

Michaelis-Menten: v = Vmax[S]/(Km + [S]); at [S] = Km the reaction velocity is exactly one-half of Vmax.

Standard free-energy relation: ΔG° = -RT ln K; a negative ΔG° indicates a spontaneous reaction under standard conditions.

Molarity conversions require molecular weight: mg/dL × 10 ÷ MW = mmol/L for a solute of known molecular weight.

Enzyme activity is expressed in international units (U); 1 U catalyzes 1 µmol of substrate conversion per minute at stated conditions.

Carbohydrate, lipid, and protein catabolism converge on acetyl-CoA, which enters the citric acid cycle for NADH and FADH2 generation.

Reference intervals typically span the central 95% of a healthy population, leaving 2.5% of healthy values below and 2.5% above the limits.

Coefficient of variation (CV%) = (standard deviation ÷ mean) × 100; it permits comparison of precision across assays with different units.

Total analytic error = bias + 1.65 × SD approximates the 95% error bound and is compared against the total allowable error goal.

Levey-Jennings charts plot control values over time with ±1SD, ±2SD, and ±3SD limits; a single point beyond ±3SD is a rejection rule.

Westgard multirule: 1-3s is a warning; 2-2s, R-4s, 4-1s, and 10x violations indicate random or systematic error requiring rejection.

Analytic sensitivity is the lowest analyte concentration distinguishable from zero; analytic specificity is the ability to measure only the intended analyte.

Delta checks compare a current result with the patient's prior value; exceeding a preset percent or absolute difference triggers specimen review.

A hemolyzed, lipemic, or icteric specimen can interfere optically or chemically; indices (H, L, I) flag such interference before reporting.

Gram-positive cells retain crystal violet-iodine due to thick peptidoglycan; gram-negative cells decolorize and counterstain pink with safranin.

Catalase converts hydrogen peroxide to water and oxygen; coagulase clots plasma and distinguishes Staphylococcus aureus from other staphylococci.

Oxidase detects cytochrome c oxidase; it is positive in Neisseria, Pseudomonas, and Aeromonas and negative in Enterobacteriaceae.

MacConkey agar selects gram-negative bacilli; lactose fermenters (E. coli, Klebsiella) produce pink colonies, non-fermenters remain colorless.

IgM is the first antibody produced in primary infection and is pentameric; IgG is monomeric, crosses the placenta, and dominates secondary responses.

IgE binds mast cells and basophils via FcεRI and mediates type I immediate hypersensitivity; IgG and IgM mediate type II and III reactions.

Complement activation proceeds by classical (IgG/IgM-antigen), alternative (microbial surfaces), or lectin (mannose-binding lectin) pathways, all converging on C3 convertase.

Bacterial growth phases are lag, log (exponential), stationary, and death; antimicrobial susceptibility testing uses log-phase organisms for standardized results.

Sodium is the major extracellular cation and potassium the major intracellular cation; hyponatremia is evaluated with serum osmolality and volume status.

Anion gap = [Na+] - ([Cl-] + [HCO3-]), normally about 8-12 mmol/L; elevated gap suggests organic acidosis, whereas normal gap suggests bicarbonate loss.

Corrected calcium (mg/dL) = measured calcium + 0.8 × (4.0 - albumin g/dL) when albumin is abnormal.

HbA1c reflects mean glucose over roughly 120 days; estimated average glucose (mg/dL) ≈ 28.7 × A1c - 46.7.

Complete blood count indices: MCV = (Hct ÷ RBC) × 10; MCH = Hb ÷ RBC × 10; MCHC = Hb ÷ Hct × 100.

Iron deficiency anemia is microcytic with low ferritin and high TIBC; anemia of chronic disease is normocytic with low TIBC and normal-to-high ferritin.

Platelet count and coagulation studies: PT evaluates extrinsic and common pathways, aPTT evaluates intrinsic and common pathways, and both are prolonged in common-pathway defects.

Prothrombin time is reported as INR = (patient PT ÷ mean normal PT)^ISI, standardizing warfarin monitoring across thromboplastin reagents.

Informed consent requires disclosure of purpose, risks, benefits, alternatives, and the patient's right to refuse or withdraw at any time.

Patient confidentiality may be breached only when legally mandated (reportable communicable disease, suspected abuse, court order) or to prevent serious imminent harm.

Competence and scope of practice: personnel perform only tests for which they are trained, credentialed, and authorized by laboratory policy.

Research involving human subjects requires institutional review board approval and adherence to the Declaration of Helsinki and Belmont principles.

Error disclosure: clinically significant erroneous results must be corrected, documented, and communicated promptly to the responsible clinician.

Conflict of interest and gift acceptance are governed by institutional policy; financial interests that could bias judgment must be disclosed.

Genetic and HIV-related results carry heightened privacy protections; unauthorized disclosure may trigger statutory penalties and licensure action.

Quality indicators include turnaround time, specimen rejection rate, corrected report rate, and proficiency testing performance.

Turnaround time is measured from order or collection to result verification; monitor the 90th percentile rather than the mean to capture outliers.

Six Sigma metric = (total allowable error - bias) ÷ SD; higher sigma indicates fewer defects and less need for intensive quality control.

Proficiency testing failures require root-cause analysis, corrective action, and documentation; two consecutive failures may trigger regulatory sanction.

Staffing calculations use workload units (test volume × time per test) divided by productive hours per full-time equivalent.

Inventory control applies reorder points and safety stock; expired reagents must be segregated and documented as removed from service.

Cost per test = (reagent cost + labor cost + overhead allocation) ÷ number of reportable tests performed.

Competency assessment of testing personnel is documented at defined intervals and includes direct observation, result review, and blind sample testing.

Standard precautions treat all blood and body fluids as potentially infectious; gloves, gowns, and eye protection are used per task risk.

Chemical hazard communication requires safety data sheets (SDS), container labeling, and staff training under OSHA Hazard Communication.

Biological safety levels: BSL-2 applies to most clinical specimens; BSL-3 applies to agents transmissible by aerosol such as M. tuberculosis cultures.

Formaldehyde, xylene, and glutaraldehyde require fume hoods or ventilators; exposure limits are documented in the SDS and monitored.

Chemical spill response: evacuate and ventilate, use the appropriate spill kit, and never use water on acid spills without consulting the SDS.

Sharps are discarded immediately into rigid, puncture-resistant, closable containers; recapping by hand is prohibited.

Fire safety uses the RACE sequence (rescue, alarm, confine, extinguish/evacuate); PASS covers extinguisher operation (pull, aim, squeeze, sweep).

Needlestick or splash exposure requires immediate washing, reporting, and post-exposure evaluation for HIV, hepatitis B, and hepatitis C within institutional timelines.