How should a laboratory handle its external quality assessment (proficiency testing) samples?

Test them like patient samples, by the usual staff

Recalibrate the analyzer just before testing them

Agree results with another laboratory before submitting

Have the most senior scientist test them in triplicate

ISO 15189 is the international standard that sets requirements for:

Quality and competence of medical laboratories

Quality management in any organization

Competence of testing and calibration labs

Safety management in medical laboratories

An internal audit finds that a reagent refrigerator's temperatures were not recorded on three weekends. Recording is restarted and the stored reagents are checked. Under ISO 15189, which further step is the corrective action?

Find why weekend checks are missed and fix the process

Fill in the missing readings from the usual values

Record the finding and close it at the next internal audit

Discard every reagent stored in that refrigerator

A laboratory's glucose EQA results (laboratory / peer mean, mmol/L) are: sample 1, 4.2 / 4.3; sample 2, 7.9 / 8.0; sample 3, 15.1 / 5.6; sample 4, 5.5 / 15.3; sample 5, 11.2 / 11.1. Internal QC was in control. The most likely cause of the two failures is:

Samples 3 and 4 were swapped or mis-transcribed

A matrix effect of the EQA material

A proportional calibration bias in the method

Random imprecision of the glucose analyzer

Accreditation, proficiency testing and DOH standards

6 DOH Abu Dhabi (HAAD) lab licensing practice questions on Accreditation, proficiency testing and DOH standards, part of General Laboratory, Quality and Safety. The first 6 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
An EQA sample has an assigned sodium value of 141 mmol/L and an SD for proficiency assessment of 2.0 mmol/L. The laboratory reports 146 mmol/L. The scheme scores |z| ≤ 2 as satisfactory, 2 to 3 as questionable and ≥ 3 as unsatisfactory. How is the result scored?
1. Az = +1.25, satisfactory
2. Bz = +2.5, questionable
3. Cz = -2.5, questionable
4. Dz = +5.0, unsatisfactory
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Answer: B · z = +2.5, questionable
z = (laboratory result - assigned value) / SD for proficiency assessment = (146 - 141) / 2.0 = +2.5. A z-score between 2 and 3 is a warning signal in ISO 13528 scoring: not a failure, but it should be reviewed, especially if it recurs. The positive sign shows that the laboratory reads high. A z-score of 3 or more is an action signal that needs a documented investigation.
- A: 1.25 divides the difference by 2 SD (4.0) instead of 1 SD.
- C: The sign is reversed; a result above the assigned value gives a positive z.
- D: 5.0 is the difference in mmol/L, not divided by the SD.
Question 2 · Easy
How should a laboratory handle its external quality assessment (proficiency testing) samples?
1. ARecalibrate the analyzer just before testing them
2. BAgree results with another laboratory before submitting
3. CHave the most senior scientist test them in triplicate
4. DTest them like patient samples, by the usual staff
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Answer: D · Test them like patient samples, by the usual staff
EQA is meant to show how the laboratory performs on everyday samples, so survey samples are put into the routine workload and tested by the staff who normally do the test, with the usual methods and number of replicates. Special treatment, such as extra replicates or a recalibration just before testing, makes the result unrepresentative. ISO 15189 and CAP forbid discussing EQA samples with other laboratories before the results are submitted. When results come back, the laboratory reviews them and investigates any that are unacceptable.
- A: Recalibrating only for EQA hides the method's real day-to-day performance.
- B: Communicating with other participants before submission is prohibited.
- C: Extra replicates by a senior scientist do not reflect routine performance.
Question 3 · Easy
ISO 15189 is the international standard that sets requirements for:
1. AQuality management in any organization
2. BQuality and competence of medical laboratories
3. CCompetence of testing and calibration labs
4. DSafety management in medical laboratories
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Answer: B · Quality and competence of medical laboratories
ISO 15189 (current edition 2022) covers both the quality management system and the technical competence of medical laboratories, across the pre-examination, examination and post-examination processes. Since 2022 it also includes the requirements for point-of-care testing that were previously in ISO 22870. Accreditation bodies assess medical laboratories against it. ISO 15190 deals with laboratory safety, ISO/IEC 17025 with testing and calibration laboratories in general, and ISO 9001 with quality management in any organization.
- A: ISO 9001 is the general quality management standard for any organization.
- C: General testing and calibration laboratories are covered by ISO/IEC 17025.
- D: Safety in medical laboratories is the subject of ISO 15190.
Question 4 · Medium
An internal audit finds that a reagent refrigerator's temperatures were not recorded on three weekends. Recording is restarted and the stored reagents are checked. Under ISO 15189, which further step is the corrective action?
1. AFill in the missing readings from the usual values
2. BRecord the finding and close it at the next internal audit
3. CDiscard every reagent stored in that refrigerator
4. DFind why weekend checks are missed and fix the process
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Answer: D · Find why weekend checks are missed and fix the process
ISO 15189 separates a correction, the immediate fix of the nonconformity (here, restarting the records and checking the reagents), from a corrective action, which removes the root cause so that the problem does not recur. Root-cause analysis might show, for example, that no one is assigned the task at weekends; the fix could be a rota or a continuous temperature alarm. The effectiveness of the action is then reviewed. Back-filling records with assumed values would be falsification.
- A: Entering assumed readings falsifies the record and fixes nothing.
- B: Recording a finding without addressing its cause is not a corrective action.
- C: Discarding reagents is at most a correction, and may not be needed if checks show no harm.
Question 5 · Hard
A laboratory's glucose EQA results (laboratory / peer mean, mmol/L) are: sample 1, 4.2 / 4.3; sample 2, 7.9 / 8.0; sample 3, 15.1 / 5.6; sample 4, 5.5 / 15.3; sample 5, 11.2 / 11.1. Internal QC was in control. The most likely cause of the two failures is:
1. AA matrix effect of the EQA material
2. BA proportional calibration bias in the method
3. CRandom imprecision of the glucose analyzer
4. DSamples 3 and 4 were swapped or mis-transcribed
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Answer: D · Samples 3 and 4 were swapped or mis-transcribed
Samples 1, 2 and 5 agree closely with the peers across the range, so the method shows no meaningful bias or imprecision. The results for samples 3 and 4 match each other's peer means almost exactly, which points to a clerical or handling error: the vials were swapped, or the results were entered against the wrong sample numbers. The investigation starts with the worksheets, vial labels and data entry. The failure still counts, and the process is corrected, for example by double-checking entries before submission.
- A: A matrix effect would affect results relative to peers in a consistent way, not reverse two samples.
- B: A calibration bias would affect all five samples, not two.
- C: Random error would not make two results match each other's targets so exactly.
Question 6 · Easy
What is proficiency testing (external quality assessment)?
1. ADoing routine instrument maintenance and checks
2. BRunning the laboratory's own daily internal controls
3. CTesting outside samples and comparing results with other labs
4. DCalibrating an analyzer against the manufacturer's calibrators
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Accreditation, proficiency testing and DOH standards

An EQA sample has an assigned sodium value of 141 mmol/L and an SD for proficiency assessment of 2.0 mmol/L. The laboratory reports 146 mmol/L. The scheme scores |z| ≤ 2 as satisfactory, 2 to 3 as questionable and ≥ 3 as unsatisfactory. How is the result scored?

How should a laboratory handle its external quality assessment (proficiency testing) samples?

ISO 15189 is the international standard that sets requirements for:

An internal audit finds that a reagent refrigerator's temperatures were not recorded on three weekends. Recording is restarted and the stored reagents are checked. Under ISO 15189, which further step is the corrective action?

A laboratory's glucose EQA results (laboratory / peer mean, mmol/L) are: sample 1, 4.2 / 4.3; sample 2, 7.9 / 8.0; sample 3, 15.1 / 5.6; sample 4, 5.5 / 15.3; sample 5, 11.2 / 11.1. Internal QC was in control. The most likely cause of the two failures is:

What is proficiency testing (external quality assessment)?