Medical Laboratory Technician Exam Laboratory Operations and QC 2 — Questions and Answers
Question 1: A Levey-Jennings chart shows a series of 6 consecutive QC results trending upward across the mean. What rule does this violate?
- 1-2s rule
- R-4s rule
- 10-x rule (Correct answer)
- 1-3s rule
Correct answer: 10-x rule
The 10-x rule is violated when 10 consecutive results fall on the same side of the mean or show a progressive trend.
Question 2: Which of the following best describes 'precision' in laboratory testing?
- Closeness of results to the true value
- Reproducibility of repeated measurements (Correct answer)
- Ability to detect low analyte concentrations
- Agreement between two different methods
Correct answer: Reproducibility of repeated measurements
Precision refers to the reproducibility or repeatability of results when the same sample is tested multiple times.
Question 3: When performing a delta check, the laboratory compares a patient's current result to:
- The laboratory reference range
- The previous result from the same patient (Correct answer)
- The QC mean for that analyte
- Results from a proficiency testing survey
Correct answer: The previous result from the same patient
Delta checks compare a patient's current result to their previous result to detect specimen identification errors or abrupt clinical changes.
Question 4: A reagent blank is used in spectrophotometry to:
- Set 100% transmittance with the solvent and reagents only (Correct answer)
- Calibrate the wavelength selector
- Measure the absorbance of the unknown sample
- Determine the linear range of the assay
Correct answer: Set 100% transmittance with the solvent and reagents only
A reagent blank zeroes out absorbance contributed by reagents alone so that only the analyte of interest is measured.
Question 5: Which type of error causes all results to shift consistently in one direction from the true value?
- Random error
- Systematic error (Correct answer)
- Gross error
- Proportional error
Correct answer: Systematic error
Systematic error (bias) causes a consistent, directional deviation of all results from the true value.
Question 6: The coefficient of variation (CV) is calculated as:
- (Mean / SD) × 100
- (SD / Mean) × 100 (Correct answer)
- (SD / Range) × 100
- (Mean − SD) × 100
Correct answer: (SD / Mean) × 100
CV = (SD / Mean) × 100, expressing precision as a percentage relative to the mean.
Question 7: CLIA mandates that proficiency testing samples must be tested:
- In duplicate by two different analysts
- Using the same routine workflow as patient samples (Correct answer)
- Only by the laboratory director
- Immediately upon receipt without storage
Correct answer: Using the same routine workflow as patient samples
CLIA requires PT samples to be processed using the same routine methods and personnel used for patient samples to ensure validity.
Medical Laboratory Technician Exam Laboratory Operations and QC 2
A Levey-Jennings chart shows a series of 6 consecutive QC results trending upward across the mean.
What rule does this violate?