LTP12 cheat sheet

Quality management system hierarchy: quality manual → standard operating procedures → work instructions → forms and records; each level must trace upward to the level above.

Biosafety levels: BSL-1 nonpathogenic; BSL-2 agents of moderate hazard with BSL-2 cabinet and restricted access; BSL-3 aerosol-transmitted agents with directional airflow and respiratory protection; BSL-4 dangerous/exotic agents with positive-pressure suit.

Chemical hazard communication requires a Safety Data Sheet in 16 sections; Sections 1-8 cover identification, hazards, composition, first aid, firefighting, accidental release, handling/storage, and exposure controls.

Sharps and biohazardous waste are segregated at point of generation; chemical waste streams are never combined unless compatibility is documented.

Document control rule: only current versions are in use, obsolete documents are removed or clearly marked, and each controlled document carries a unique identifier, version, and effective date.

Competency assessment occurs at initial hire, after policy or method change, and at least annually thereafter; direct observation plus blind sample testing is typical.

Error rate formula: percent error = (measured − true) / true × 100; relative error uses the same expression and is reported without units.

Spill response sequence: alert and evacuate, secure the area, don PPE, contain, disinfect or absorb with appropriate agent, then verify and document.

Order of draw for skin puncture: discard first drop, then EDTA, other additive tubes, serum tubes, and heparin last to limit tissue-fluid and additive carryover.

Tourniquet application should not exceed one minute; prolonged stasis raises potassium, lactate, and total protein and alters protein-bound analytes.

Hemolysis falsely increases potassium, LDH, AST, and phosphate, and falsely decreases glucose and bilirubin depending on method; document and recollect when interference is significant.

Additive inversion counts after collection: EDTA and heparin tubes 8-10 inversions, serum separator 5, citrate 3-4; citrate tubes must fill to the indicated line for a 9:1 blood-to-anticoagulant ratio.

Transport stability rules: ammonia and blood gases on ice and analyzed promptly; light-sensitive analytes (bilirubin, vitamin B12) protected from light; cryoglobulin and cold agglutinin specimens kept at 37 °C until separation.

Centrifugation for serum/plasma is typically 10-15 minutes at 1000-1200 × g at controlled temperature; incomplete clotting causes fibrin strands and instrument probe obstruction.

24-hour urine collection requires a documented start and end time, proper preservative, and total volume; results are reported as concentration × volume per time period.

Rejection criteria include unlabeled or mislabeled containers, gross hemolysis, insufficient volume, expired collection devices, and unapproved transport temperature deviations.

Validation establishes performance for a new in-house method; verification confirms that a manufacturer's validated method performs as claimed in the local laboratory.

Precision components: repeatability (within-run), intermediate precision (within-laboratory, across days/operators), and reproducibility (across laboratories); report as SD and CV percent.

CV percent = (SD / mean) × 100; compare observed CV against the laboratory's defined acceptance limit derived from biologic variation or manufacturer claims.

Accuracy is assessed by recovery studies, comparison with a reference method (Deming or Passing-Bablok regression), or bias against a certified reference material.

Linearity is evaluated across at least five concentration levels spanning the reportable range; deviation from linearity must remain within the laboratory's stated tolerance.

Limit of detection is the lowest amount detectable with stated confidence; limit of quantification is the lowest amount meeting predefined precision and bias goals.

Analytical measurement range is the interval producing results within acceptable accuracy and precision without dilution; clinical reportable range may extend it by validated dilution.

Interference testing evaluates endogenous substances (hemoglobin, bilirubin, lipids) and common drugs at defined concentrations; results are documented as percent bias at each level.

Westgard multirule: 1-2s is a warning; 1-3s, 2-2s, R-4s, and 4-1s are rejection rules; 10x indicates systematic shift and is a rejection rule in most schemes.

Levey-Jennings chart plots control values over time against mean and ±1s, ±2s, ±3s limits; shifts are abrupt mean changes while trends are six or more consecutive values in one direction.

Calibration establishes the relationship between signal and concentration using calibrators; calibration verification confirms that relationship with independent materials at multiple levels.

Proficiency testing requires results be handled as patient samples, not shared between analysts, and not referred to another laboratory; unacceptable results trigger investigation and corrective action.

Control material selection: matrix should resemble patient samples, analyte levels should span medical decision points, and lot changes require establishment of new means and SDs.

Random error raises imprecision and triggers 1-3s or R-4s; systematic error shifts the mean and triggers 2-2s, 4-1s, or 10x.

Sigma metric = (TEa − |bias|) / CV; higher sigma indicates fewer QC rules are needed, and lower sigma requires tighter rules or more frequent QC.

Documented QC review must precede patient result release; out-of-control runs require corrective action, documentation, and repeat testing before reporting.

Beer-Lambert law: absorbance = molar absorptivity × path length × concentration; photometric methods are valid only in the linear absorbance region, generally below about 2.0 AU.

Spectrophotometer components in order: light source → monochromator → cuvette → photodetector → signal processor; stray light limits the upper measurable absorbance.

Ion-selective electrodes measure activity, not concentration; the Nernst equation relates potential to the logarithm of ion activity, and ionic strength affects results.

Potentiometric pH and blood gas analyzers use separate electrodes for pH, pCO2 (Severinghaus), and pO2 (Clark); each requires periodic two-point calibration.

Immunoassay formats include competitive (small analytes, signal inversely proportional to concentration) and sandwich (large analytes, signal directly proportional); the hook effect causes falsely low results at very high concentration.

Chromatography separates by differential partitioning between mobile and stationary phases; retention time identifies and peak area quantifies.

Mass spectrometry quantifies by mass-to-charge ratio; internal standards correct for ionization variability and matrix effects.

Osmolality by freezing point depression measures total particle concentration; the osmolal gap is measured osmolality minus calculated osmolality, normally under about 10 mOsm/kg.

Reference intervals are established from at least 120 healthy reference individuals per partition; the central 95 percent interval spans the 2.5th to 97.5th percentiles.

Partitioning by age and sex is justified when the difference between subgroup means or intervals is clinically and statistically meaningful.

Delta check compares a current result to a prior result from the same patient using an absolute or percentage threshold; failure triggers specimen review before reporting.

Critical values must be reported promptly with documented read-back of patient identifier, test, result, and the name of the person receiving it.

Calculated results (LDL cholesterol by Friedewald, anion gap, osmolality, eGFR) must be suppressed or flagged when input values fall outside the formula's validated range.

Results below the limit of detection are reported as less than that value, not as zero; results above the analytical range require validated dilution and a dilution factor notation.

Autoverification rules must be validated before use and must include range checks, delta checks, interference flags, and QC status before release.

Rounding and significant figures follow the measuring instrument's resolution; unit conversions must be verified, for example glucose mg/dL × 0.0555 = mmol/L.

CLIA categorizes tests as waived, moderate, or high complexity; laboratories hold a certificate appropriate to the testing performed and are subject to unannounced surveys.

Patient confidentiality rules prohibit disclosure of identifiable results without authorization except where required by law, public health reporting, or for treatment.

Research involving human specimens requires institutional review board approval and informed consent unless the protocol qualifies for exemption.

Method performance documentation must be retained per the laboratory's record retention policy, commonly at least two years for quality records and longer for some regulated records.

Conflict of interest must be disclosed when an employee has a financial interest in a vendor, test, or referral relationship.

Competency and proficiency testing records are personnel records; falsification of results or QC is a reportable integrity violation.

Specimen and result ownership: the laboratory owns records, the patient owns the information; release follows authorization and applicable privacy regulation.

Error disclosure: clinically significant errors are communicated to the responsible clinician promptly and documented, regardless of whether harm occurred.

Root cause analysis tools: five whys, fishbone (cause-and-effect) diagram, and fault tree; the goal is to distinguish proximate from underlying causes.

Corrective action addresses the cause of a detected nonconformity; preventive action addresses a potential nonconformity before it occurs.

Investigation sequence for an aberrant result: verify specimen identity and integrity, review QC and calibration, inspect reagent and instrument status, then repeat the test.

Random error is suggested by scattered control values on both sides of the mean; systematic error is suggested by consecutive values on one side or a step change.

Hook effect is suspected when a result is unexpectedly low in a patient with clinical findings of high analyte; repeat after dilution to confirm.

Carryover is tested by running a high-concentration sample followed by a low-concentration sample; a positive bias in the low sample indicates carryover.

Corrective action effectiveness must be verified and documented, and the action closed only after monitoring shows the problem has not recurred.

Turnaround time failures are analyzed by timestamp audit at each phase: collection, receipt, analysis, and reporting, to locate the delay.