CMT Laboratory Quality Control and Management 1 — Questions and Answers
Question 1: What is the primary purpose of running quality control (QC) samples in a clinical laboratory?
- To calibrate analytical instruments
- To monitor the precision and accuracy of test results (Correct answer)
- To train new laboratory staff on procedures
- To document and archive patient results
Correct answer: To monitor the precision and accuracy of test results
QC samples are run to monitor the precision and accuracy of analytical processes and detect errors before patient results are reported.
Question 2: Which Westgard rule is triggered when a single control value exceeds the mean ± 3 standard deviations, indicating a random error?
- 2₂s rule
- R₄s rule
- 1₃s rule (Correct answer)
- 4₁s rule
Correct answer: 1₃s rule
The 1₃s rule is a rejection rule triggered when one control observation exceeds the mean ± 3 SD, indicating a possible random error.
Question 3: In laboratory quality management, what does 'accuracy' specifically refer to?
- The reproducibility of repeated measurements under the same conditions
- How close a measurement is to the true or accepted reference value (Correct answer)
- The range of values that includes 95% of a reference population
- The lowest analyte concentration an instrument can reliably detect
Correct answer: How close a measurement is to the true or accepted reference value
Accuracy refers to how closely a measured value agrees with the true or accepted reference value.
Question 4: What does the coefficient of variation (CV) primarily assess in laboratory quality control?
- Accuracy of a method compared to a reference method
- Bias between two analytical methods
- Imprecision (random error) of an analytical method (Correct answer)
- The linearity of an assay across its reportable range
Correct answer: Imprecision (random error) of an analytical method
The coefficient of variation (CV = SD/mean × 100%) is a measure of imprecision or random error expressed as a percentage of the mean.
Question 5: Which federal agency administers and enforces CLIA regulations for clinical laboratory quality standards in the United States?
- The Joint Commission (TJC)
- College of American Pathologists (CAP)
- Centers for Medicare & Medicaid Services (CMS) (Correct answer)
- American Society for Clinical Pathology (ASCP)
Correct answer: Centers for Medicare & Medicaid Services (CMS)
The Centers for Medicare & Medicaid Services (CMS) administers and enforces CLIA regulations that establish quality standards for clinical laboratories.
Question 6: When a Westgard 2₂s rule is triggered (two consecutive controls exceed ±2 SD in the same direction), what type of error is most likely present?
- Random error
- Systematic error (Correct answer)
- Gross error
- Pre-analytical error
Correct answer: Systematic error
The 2₂s rule, where two consecutive controls exceed ±2 SD in the same direction, is indicative of systematic error such as a shift or drift in the method.
Question 7: What is the primary purpose of proficiency testing (PT) in clinical laboratories?
- To evaluate individual laboratory employee competency
- To compare a laboratory's performance with peer laboratories using unknown samples (Correct answer)
- To validate new equipment before it is placed into service
- To establish reference ranges for newly implemented assays
Correct answer: To compare a laboratory's performance with peer laboratories using unknown samples
Proficiency testing involves external agencies sending unknown samples to laboratories so their performance can be compared against peer laboratories and accepted values.
CMT Laboratory Quality Control and Management 1
What is the primary purpose of running quality control (QC) samples in a clinical laboratory?