CLC Quality Control & Process Improvement 3 — Questions and Answers
Question 1: A laboratory implements a new analyzer and finds the coefficient of variation (CV) for a high-concentration QC material is 2.5% but 8.1% for a low-concentration QC material. This pattern MOST likely indicates:
- Proportional random error
- Constant random error (Correct answer)
- Systematic bias at all levels
- Carryover contamination
Correct answer: Constant random error
High CV at low concentrations with acceptable CV at high concentrations is characteristic of constant (absolute) imprecision, which has proportionally more impact near the detection limit.
Question 2: Which document type in a laboratory quality management system describes the step-by-step instructions for performing a specific analytical procedure?
- Quality manual
- Standard operating procedure (SOP) (Correct answer)
- Policy document
- Work instruction
Correct answer: Standard operating procedure (SOP)
Standard operating procedures (SOPs) provide detailed, step-by-step instructions for performing specific laboratory tasks or analytical procedures.
Question 3: A Pareto analysis of laboratory errors reveals that specimen labeling errors, centrifugation problems, and wrong tube type together account for 78% of all pre-analytical errors. This finding supports which principle?
- The Central Limit Theorem
- The 80/20 rule (Correct answer)
- The Law of Large Numbers
- Gaussian distribution
Correct answer: The 80/20 rule
The Pareto principle (80/20 rule) states that approximately 80% of effects come from 20% of causes, guiding prioritization of improvement efforts.
Question 4: During proficiency testing (PT), a laboratory's result for a serum sodium sample is flagged as unacceptable. The FIRST action the laboratory director should take is:
- Immediately retest the PT sample
- Investigate the cause through root cause analysis (Correct answer)
- Report the failure to the accrediting body
- Switch to a new analyzer
Correct answer: Investigate the cause through root cause analysis
Root cause analysis must be performed first to identify why the PT failure occurred before corrective action can be appropriately targeted.
Question 5: In a laboratory QC program, what is the PRIMARY purpose of using two levels of controls (normal and abnormal)?
- To satisfy accreditation requirements only
- To detect errors across the analytical measurement range (Correct answer)
- To reduce the number of patient specimens tested
- To replace calibration verification requirements
Correct answer: To detect errors across the analytical measurement range
Running QC at both normal and abnormal concentrations verifies method performance across clinically relevant portions of the analytical measurement range.
Question 6: A laboratory's turnaround time data shows a normal distribution with mean 45 minutes and SD 8 minutes. What percentage of results will be reported within 29–61 minutes?
- 68%
- 95% (Correct answer)
- 99.7%
- 50%
Correct answer: 95%
The range 29–61 minutes spans ±2 SD from the mean (45 ± 16), which encompasses approximately 95% of values in a normal distribution.
Question 7: Which quality indicator is MOST useful for monitoring laboratory pre-analytical errors related to sample integrity?
- Turnaround time
- Hemolysis index tracking (Correct answer)
- QC failure rate
- Reagent cost per test
Correct answer: Hemolysis index tracking
Tracking hemolysis index rates identifies pre-analytical problems with blood collection, transport, and processing that compromise specimen integrity.
CLC Quality Control & Process Improvement 3
A laboratory implements a new analyzer and finds the coefficient of variation (CV) for a high-concentration QC material is 2.5% but 8.1% for a low-concentration QC material.
This pattern MOST likely indicates: