CMLA Quality Control & Assurance in Laboratory Practices 4 — Questions and Answers
Question 1: Which of the following is an example of a pre-analytical error that would affect QC and patient results?
- Instrument calibration failure
- Hemolyzed specimen due to improper venipuncture technique (Correct answer)
- Incorrect control value entry on the QC chart
- Reagent stored at wrong temperature
Correct answer: Hemolyzed specimen due to improper venipuncture technique
Hemolysis caused by improper collection is a pre-analytical error that interferes with multiple analytes before the specimen even reaches the analyzer.
Question 2: What is the primary function of an internal quality control (IQC) material compared to external proficiency testing (PT)?
- IQC monitors day-to-day analytical performance; PT compares performance against peer laboratories (Correct answer)
- IQC is required only for high-complexity tests; PT is required only for waived tests
- IQC replaces the need for PT in accredited laboratories
- PT monitors daily performance; IQC is used only for annual certification
Correct answer: IQC monitors day-to-day analytical performance; PT compares performance against peer laboratories
IQC monitors the consistency and accuracy of testing on a daily basis, while PT benchmarks a laboratory's performance against other labs using the same method.
Question 3: A laboratory discovers that control results for a coagulation analyzer passed QC, but several patient PT/INR results appear unusually high. What should be done first?
- Report the patient results since QC passed
- Investigate a possible matrix effect or pre-analytical issue with patient samples (Correct answer)
- Immediately recalibrate the analyzer and repeat QC
- Notify the billing department of the discrepancy
Correct answer: Investigate a possible matrix effect or pre-analytical issue with patient samples
Passing QC does not rule out pre-analytical problems or matrix effects in patient specimens; clinical correlation and sample investigation are needed.
Question 4: Which statistical measure best represents the day-to-day variability of a QC control material?
- Mean
- Coefficient of variation (CV) (Correct answer)
- Median
- Reference range
Correct answer: Coefficient of variation (CV)
The CV expresses standard deviation as a percentage of the mean, making it the best measure for comparing variability across different analytes or concentrations.
Question 5: According to CLIA regulations, how long must a laboratory retain QC records?
- 6 months
- 1 year
- 2 years (Correct answer)
- 5 years
Correct answer: 2 years
CLIA requires laboratories to retain QC records for a minimum of 2 years to allow review during inspections and accreditation surveys.
Question 6: A laboratory is implementing a new hematology analyzer. Which validation study specifically confirms the analyzer produces equivalent results to the current method?
- Linearity study
- Method comparison study (Correct answer)
- Reference interval verification
- Imprecision study
Correct answer: Method comparison study
A method comparison study tests patient samples on both analyzers simultaneously to confirm the new instrument produces clinically equivalent results.
Question 7: Which of the following would cause a violation of the 2-2s Westgard rejection rule?
- Two consecutive control values both exceeding +2s or both exceeding -2s (Correct answer)
- One control value exceeding ±2s followed by one within ±1s
- A single control value exceeding ±3s
- The range between two controls within one run exceeding 4s
Correct answer: Two consecutive control values both exceeding +2s or both exceeding -2s
The 2-2s rule is violated when two consecutive QC values both exceed ±2 standard deviations on the same side of the mean, indicating systematic error.
CMLA Quality Control & Assurance in Laboratory Practices 4
Which of the following is an example of a pre-analytical error that would affect QC and patient results?