USCIS Quality Control & Assurance 3 — Questions and Answers
Question 1: A batch of QuantiFERON-TB Gold Plus (QFT-Plus) tests shows that the nil tube OD value is 0.8 IU/mL, exceeding the manufacturer's cutoff of 0.70. What is the appropriate response?
- Subtract the excess from all patient results and report normally
- Declare the results invalid for those specimens and retest if possible (Correct answer)
- Report results as positive for all affected patients
- Ignore the nil value if the TB antigen tube shows high reactivity
Correct answer: Declare the results invalid for those specimens and retest if possible
An elevated nil tube suggests nonspecific stimulation or contamination, invalidating those specimens per manufacturer criteria.
Question 2: How often must a CLIA-certified laboratory performing I-693 testing document refrigerator temperature logs?
- Once per week
- Once per month
- At least once per day when reagents or specimens are stored (Correct answer)
- Only when a temperature alarm is triggered
Correct answer: At least once per day when reagents or specimens are stored
CLIA regulations require temperature monitoring at least once daily to ensure storage conditions remain within acceptable ranges.
Question 3: A civil surgeon clinic receives a proficiency testing (PT) sample for syphilis serology and tests it as a routine patient specimen. The result is graded as unacceptable. What corrective action is required?
- Dispute the grading with the PT provider
- Perform root cause analysis and document corrective action taken (Correct answer)
- Retest the PT sample using a different method and report the new result
- No action needed since PT failures are permitted twice per year
Correct answer: Perform root cause analysis and document corrective action taken
PT failures require documented root cause analysis and corrective action to maintain CLIA certification.
Question 4: In the context of USCIS medical examinations, what is the significance of lot-to-lot verification when switching to a new reagent lot?
- It is only required for FDA-cleared devices
- It ensures the new lot performs equivalently to the previous lot before patient samples are tested (Correct answer)
- It allows the lab to skip quality control runs for one day
- It is performed by the manufacturer before shipment, so no in-house verification is needed
Correct answer: It ensures the new lot performs equivalently to the previous lot before patient samples are tested
Lot-to-lot verification confirms that a new reagent lot produces results consistent with the established method before use on patients.
Question 5: Which of the following is an example of a pre-analytical quality control step in the I-693 laboratory process?
- Calibrating the ELISA plate reader
- Verifying patient identity and checking specimen labeling before testing (Correct answer)
- Reviewing reference ranges used in the report
- Documenting the lot number of the control serum
Correct answer: Verifying patient identity and checking specimen labeling before testing
Pre-analytical quality control includes all steps before testing begins, such as verifying specimen identity and integrity.
Question 6: A civil surgeon's lab uses Levey-Jennings charts to track QC data. Over 10 days, the control values gradually shift upward but remain within 2 SD. What does this trend indicate?
- Random analytical error requiring no action
- A systematic error such as reagent deterioration or instrument drift (Correct answer)
- A correct drift caused by seasonal temperature changes in the lab
- Normal biological variation in the control material
Correct answer: A systematic error such as reagent deterioration or instrument drift
A gradual directional shift on a Levey-Jennings chart indicates systematic error, often from deteriorating reagents or instrument drift.
Question 7: Under CLIA, what is the minimum frequency for calibration verification of a quantitative test used in I-693 examinations?
- Daily
- Every 6 months or when recommended by the manufacturer, or when certain events occur (Correct answer)
- Only at initial instrument setup
- Every 2 years
Correct answer: Every 6 months or when recommended by the manufacturer, or when certain events occur
CLIA requires calibration verification at least every 6 months or per manufacturer instructions and after specific triggering events.
USCIS Quality Control & Assurance 3
A batch of QuantiFERON-TB Gold Plus (QFT-Plus) tests shows that the nil tube OD value is 0.8 IU/mL, exceeding the manufacturer's cutoff of 0.70.
What is the appropriate response?