Quality Assurance and Accreditation
Quality assurance questions test the difference between checking a result and proving a process: internal QC, external assessment, validation, documentation and the corrective-action loop.
Core rules
- Internal QC runs with each batch and monitors precision and stability against defined limits; EQA or proficiency testing is periodic and compares your result with peer laboratories to detect bias.
- Levey–Jennings charts display QC results over time with mean and standard deviation. Westgard rules: 1-2s is a warning; 1-3s, 2-2s, R-4s, 4-1s and 10x are rejection rules.
- Calibration establishes the relationship between signal and concentration; verification confirms the method meets specified performance in your own laboratory.
- Validation parameters: accuracy, precision (repeatability and within-laboratory), linearity or measuring interval, limit of detection and quantification, analytical specificity and interference, carryover, reference interval, sample stability.
- Measurement uncertainty combines imprecision and bias and is reported with a coverage factor (k = 2, approximately 95%).
- ISO 15189 is the international standard for medical laboratories, addressing competence, impartiality, consistent operation, and the pre-examination, examination and post-examination processes including point-of-care testing.
- Nonconformity management: immediate correction, root cause analysis (five whys, fishbone), corrective and preventive action, then a documented effectiveness check.
- Documents need a unique identifier, version, approval, controlled distribution, review date and withdrawal of superseded copies.
- Audit identifies nonconformities; it does not replace IQC or EQA.
Worked example
At the start of a shift one QC level gives a single point beyond 2 SD but within 3 SD, and the other level is within limits. This is a 1-2s warning, not automatic rejection: inspect the chart for a trend or shift, check reagents and calibration, and repeat the level. If the next point exceeds 3 SD, or two consecutive points fall beyond 2 SD on the same side, reject the run and investigate before releasing patient results.
Traps
- Repeating an EQA sample until it looks right.
- Rejecting a run on a single 1-2s warning.
- Closing a CAPA without an effectiveness check.
- Assuming a calibrated analyser is validated for a new sample type or population.
Laboratory Safety
Safety questions test whether you can identify the hazard, apply the hierarchy of controls, and respond correctly to the incident that has already happened.
Core rules
- Controls in order of effectiveness: elimination, substitution, engineering controls (fume hood, biological safety cabinet, sharps container), administrative controls (SOPs, training, signage, immunisation), then PPE as the last line.
- Routine diagnostic work is generally BSL-2: restricted access, handwashing, PPE, autoclave, sharps policy. Aerosol-generating procedures and high-risk cultures require BSL-3 practice and a cabinet.
- Do not recap needles; dispose at the point of use into a puncture-resistant, labelled container filled to no more than three-quarters.
- Blood or body fluid spill: contain, cover with absorbent, apply sodium hypochlorite 0.5% (10,000 ppm available chlorine) or a validated disinfectant, allow contact time, remove while wearing PPE, decontaminate the area, and dispose as infectious waste.
- Segregate waste by the national colour scheme: infectious waste in marked bags, sharps in rigid containers, chemical waste separately, never compacted with general waste.
- Chemicals: read the safety data sheet, use the fume hood for formaldehyde and solvents, store flammables in approved cabinets, label secondary containers, recognise GHS pictograms.
- Fire: know the class (A solids, B liquids, C gases, D metals, electrical) and use PASS; evacuate rather than fight anything beyond a small incipient fire.
- Specimen transport outside the laboratory uses triple packaging and UN3373 Category B marking.
- Immunisation and post-exposure prophylaxis are part of the control programme, not a substitute for it.
Worked example
A nurse sustains a needlestick from a patient known to be HBsAg positive. She should wash the wound with soap and water without squeezing or sucking it, report immediately, and have the source and exposure documented. Her HBV vaccination and anti-HBs status are checked; if she is not immune, hepatitis B immunoglobulin plus vaccine should be given as soon as possible, ideally within 24 hours and up to 7 days. HIV PEP, if indicated, should start ideally within 2 hours.
Traps
- Using alcohol alone on a large blood spill; it is unreliable with high protein load.
- Assuming HIV carries the highest transmission risk; hepatitis B is higher in unvaccinated staff.
- Storing food or drink in the laboratory refrigerator.
- Doffing PPE in the wrong order and contaminating the face.
Ethics and Professional Practice
Ethics questions test whether you can act correctly when a result, a request or a mistake creates competing obligations to the patient, the requesting clinician and the record.
Core rules
- Four principles: respect for autonomy, beneficence, non-maleficence and justice. They are tools for reasoning, not labels to attach after the decision.
- Consent must be informed, voluntary, and given by a person with capacity. It covers purpose, risks, benefits, alternatives and the consequences of refusal. Consenting to venepuncture is not consent to every test that could be run on the sample.
- Genetic and HIV testing require specific, documented consent because of familial and social implications.
- Confidentiality: disclose the minimum necessary to the treating team. Results go to the requesting clinician and, where agreed, to the patient. Discussing results with relatives without consent is a breach.
- Legitimate exceptions exist, such as notifiable diseases, a court order, or serious imminent risk to others; any disclosure must be documented with the reason.
- Critical results must travel by a route that guarantees receipt: telephone the responsible clinician, obtain read-back of the value and patient identifiers, and record time, name and action taken.
- Errors require open disclosure to the patient, an incident report and a systems review. Concealment is a professional and often legal failure.
- Research needs ethics committee approval, protocol adherence and consent; conflicts of interest such as gifts, shares or paid lectures must be declared.
- Professional competence includes staying within your scope, referring, and never signing a report you did not verify.
Worked example
A potassium of 7.2 mmol/L returns at 02:00 on an emergency department sample. The correct action is to telephone the responsible clinician immediately, read back the value and patient identifiers, and document the call. A comment entered in the laboratory information system alone is not communication, and waiting for the morning round is a patient-safety failure.
Traps
- Giving results to a relative who telephones "for the family" without the patient's consent.
- Disclosing a genetic result to relatives without the patient's agreement.
- Treating a notifiable disease notification as a breach of confidentiality.
- Amending a report without leaving an audit trail.