Medical Laboratory TechnicianĀ Exam Laboratory Operations and QC 3 ā Questions and Answers
Question 1: A new lot of QC material is being validated. The laboratory should establish the mean and SD by running the QC material at least:
- 5 times over 1 day
- 10 times over 2 days
- 20 times over multiple days (Correct answer)
- 3 times on consecutive days
Correct answer: 20 times over multiple days
At least 20 replicates run over multiple days are recommended to establish reliable QC mean and SD values.
Question 2: Which specimen type is most appropriate for glucose testing when the sample cannot be processed within 30 minutes?
- Serum in a plain red-top tube
- Plasma in a sodium fluoride/potassium oxalate tube (Correct answer)
- Whole blood in an EDTA tube
- Urine in a preservative-free container
Correct answer: Plasma in a sodium fluoride/potassium oxalate tube
Sodium fluoride inhibits glycolysis, preserving glucose concentrations in plasma when processing is delayed.
Question 3: The linear range of an assay refers to the concentration interval over which:
- QC results must fall within 2 SD of the mean
- The assay produces results directly proportional to analyte concentration (Correct answer)
- The coefficient of variation is less than 5%
- Calibrators are prepared for use
Correct answer: The assay produces results directly proportional to analyte concentration
The linear range is the analyte concentration interval where instrument response is directly proportional to concentration.
Question 4: A laboratory receives a proficiency testing result of 'unacceptable' for a glucose analyte. The FIRST corrective action should be to:
- Immediately purchase a new analyzer
- Investigate the cause before resuming patient testing (Correct answer)
- Report the error to the state health department
- Repeat the PT sample on a different instrument
Correct answer: Investigate the cause before resuming patient testing
The first step after an unacceptable PT result is root cause investigation; patient testing should be evaluated for impact.
Question 5: Which of the following is an example of a pre-analytical error?
- Pipetting the wrong volume of sample into the reaction cuvette
- Incorrect calibration of the analyzer
- Hemolysis caused by difficult venipuncture (Correct answer)
- Reporting results in the wrong unit of measure
Correct answer: Hemolysis caused by difficult venipuncture
Hemolysis from traumatic venipuncture occurs before the sample reaches the analyzer, making it a pre-analytical error.
Question 6: A reference interval is established using samples from:
- Known patient populations with confirmed diagnoses
- Apparently healthy individuals representative of the test population (Correct answer)
- Previous QC runs from the same lot of control material
- Proficiency testing peer group participants
Correct answer: Apparently healthy individuals representative of the test population
Reference intervals are derived from healthy, asymptomatic individuals who represent the population for whom the test is intended.
Question 7: Under CLIA, a laboratory performing only CLIA-waived tests must:
- Enroll in proficiency testing for all analytes tested
- Follow the manufacturer's instructions for test performance (Correct answer)
- Employ a full-time laboratory director on-site
- Participate in biannual on-site inspections
Correct answer: Follow the manufacturer's instructions for test performance
CLIA-waived laboratories must follow manufacturer instructions; they are exempt from most other CLIA requirements.
Medical Laboratory TechnicianĀ Exam Laboratory Operations and QC 3
A new lot of QC material is being validated.
The laboratory should establish the mean and SD by running the QC material at least: