A 31-year-old woman attends a new outpatient clinic for a routine check. Her creatinine is 76 µmol/L (0.86 mg/dL), the same as at another clinic of the same hospital a year ago. This time the report shows an eGFR (CKD-EPI 2021) of 68 mL/min/1.73 m², flagged low, compared with 93 last year. QC was in range, and the clinic doctor phones to query the result. The laboratory system shows her date of birth as 14/05/1945; the hospital's master patient record and her identity card show 14/05/1995. What should the laboratory do?

Correct the birth date and issue a corrected report

Recollect the sample to confirm her identity

Rerun the creatinine after recalibration

Phone the correct eGFR but leave the report

A potassium of 6.9 mmol/L was released and phoned to a ward as critical. An hour later, the technologist notices that the sample's hemolysis index was high, which should have stopped the result. What is the correct action?

Tell the clinician, amend the report and ask for a new sample

Report a corrected potassium based on the hemolysis index

Delete the result from the record so it cannot be acted on

Leave the report, since the clinician has already been told

Which of these errors occurs in the post-analytical phase of testing?

A critical result phoned to the wrong ward

An expired reagent pack used on the analyzer

A sample drawn from the arm with an IV drip

A tube left unspun on the bench overnight

After an EQA failure, a laboratory finds that 40 vitamin D results reported last week were about 25% low, because a wrong calibrator value had been entered. The samples are stored frozen. What is the most appropriate action?

Retest the stored samples and issue corrected reports

Add 25% to each result and reissue the reports

Send clinicians a general notice but leave the reports

Leave the reports, since vitamin D is not urgent

A technologist phones a critical sodium of 116 mmol/L. The nurse reads back the result correctly, but the medical record number she reads from the chart differs from the one on the request. The technologist should:

Resolve the patient's identity before ending the call

End the call and send the report by e-mail instead

Accept it, since the result was read back correctly

Give the result to the ward clerk to pass on

Errors, delta checks and critical value reporting

10 DOH Abu Dhabi (HAAD) lab licensing practice questions on Errors, delta checks and critical value reporting, part of General Laboratory, Quality and Safety. The first 10 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 · Hard
A 31-year-old woman attends a new outpatient clinic for a routine check. Her creatinine is 76 µmol/L (0.86 mg/dL), the same as at another clinic of the same hospital a year ago. This time the report shows an eGFR (CKD-EPI 2021) of 68 mL/min/1.73 m², flagged low, compared with 93 last year. QC was in range, and the clinic doctor phones to query the result. The laboratory system shows her date of birth as 14/05/1945; the hospital's master patient record and her identity card show 14/05/1995. What should the laboratory do?
1. ARecollect the sample to confirm her identity
2. BCorrect the birth date and issue a corrected report
3. CRerun the creatinine after recalibration
4. DPhone the correct eGFR but leave the report
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Answer: B · Correct the birth date and issue a corrected report
The creatinine is unchanged and analytically sound, so the fall in eGFR must come from another input to the equation. CKD-EPI 2021 uses age and sex, and an age of 81 instead of 31 lowers the eGFR from about 93 to 68 for the same creatinine. The error arose when the patient was registered, a pre-analytical error that surfaced in a calculated result. The laboratory corrects the demographic record and issues a corrected report that is clearly marked as amended, with the original kept on file as ISO 15189 requires. It also informs the requesting doctor and logs the incident, so that other results registered with the wrong birth date are found and corrected.
- A: Her identity is not in doubt: the creatinine matches last year's, and only the birth date is wrong.
- C: QC was in range and the creatinine is consistent; only the age used in the calculation is wrong.
- D: A phoned result alone leaves a wrong eGFR in the permanent record.
Question 2 · Hard
A potassium of 6.9 mmol/L was released and phoned to a ward as critical. An hour later, the technologist notices that the sample's hemolysis index was high, which should have stopped the result. What is the correct action?
1. ATell the clinician, amend the report and ask for a new sample
2. BReport a corrected potassium based on the hemolysis index
3. CDelete the result from the record so it cannot be acted on
4. DLeave the report, since the clinician has already been told
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Answer: A · Tell the clinician, amend the report and ask for a new sample
Hemolysis releases potassium from red cells, so the result is invalid and the patient may already be receiving treatment for a false hyperkalemia. The clinician is called at once, the report is amended to show that the result is invalid and why, with the original kept in the audit trail, and a new sample is requested. Mathematical corrections for hemolysis are not reliable enough for patient care. The event is recorded as a nonconformity, and the step that missed the flag is reviewed.
- B: Hemolysis corrections vary between patients and are not reliable for reporting.
- C: Deleting a released result removes the audit trail and hides the error.
- D: A result known to be invalid must be corrected even after it has been acted on.
Question 3 · Medium
Which of these errors occurs in the post-analytical phase of testing?
1. AAn expired reagent pack used on the analyzer
2. BA sample drawn from the arm with an IV drip
3. CA tube left unspun on the bench overnight
4. DA critical result phoned to the wrong ward
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Answer: D · A critical result phoned to the wrong ward
The post-analytical phase runs from the release of a result to its delivery and interpretation, so reporting a result to the wrong place is a post-analytical error. Collection from a drip arm and delayed separation are pre-analytical errors, because they happen before the sample is analyzed. Using an expired reagent is an analytical error. Read-back, two identifiers and audit trails are the main defenses in the post-analytical phase.
- A: An expired reagent causes an analytical error.
- B: Drawing above an infusion is a pre-analytical collection error.
- C: Delayed centrifugation is a pre-analytical processing error.
Question 4 · Hard
After an EQA failure, a laboratory finds that 40 vitamin D results reported last week were about 25% low, because a wrong calibrator value had been entered. The samples are stored frozen. What is the most appropriate action?
1. ARetest the stored samples and issue corrected reports
2. BAdd 25% to each result and reissue the reports
3. CSend clinicians a general notice but leave the reports
4. DLeave the reports, since vitamin D is not urgent
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Answer: A · Retest the stored samples and issue corrected reports
Released reports known to be wrong must be corrected, and when the original samples are stored and stable, retesting after correct calibration gives true results. Corrected reports are clearly marked as corrected, keep the original values visible and go to the requesting clinicians, with a direct call when the change could alter treatment. A blanket 25% factor assumes the error was exactly the same for every sample, which has not been shown. The event is handled as a nonconformity, including how the wrong value came to be entered.
- B: A fixed factor assumes an exactly uniform error that has not been proven.
- C: A general notice leaves wrong results in each patient's record.
- D: Wrong results must be corrected whatever the urgency of the test.
Question 5 · Medium
A technologist phones a critical sodium of 116 mmol/L. The nurse reads back the result correctly, but the medical record number she reads from the chart differs from the one on the request. The technologist should:
1. AEnd the call and send the report by e-mail instead
2. BResolve the patient's identity before ending the call
3. CAccept it, since the result was read back correctly
4. DGive the result to the ward clerk to pass on
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Answer: B · Resolve the patient's identity before ending the call
Read-back confirms both the result and the patient it belongs to. A mismatched identifier means the nurse may be looking at another patient's chart, and treating the wrong patient for hyponatremia could cause harm. The technologist confirms two identifiers against the request, makes sure the right patient is identified, and documents who received the result and when. Critical results go directly to a licensed caregiver responsible for the patient, not to a clerk.
- A: E-mail does not ensure that a caregiver receives a critical result promptly.
- C: A correct value given for the wrong patient is still a dangerous error.
- D: Critical results go to a licensed caregiver, not to clerical staff.
Question 6 · Medium
A delta check flags a patient's hemoglobin: 68 g/L (6.8 g/dL) yesterday, 92 g/L (9.2 g/dL) today. The record shows two units of red cells were transfused overnight, and the red cell indices are unchanged. What should the technologist do?
1. AReport it to the ward as a critical value
2. BRelease the result, as the transfusion explains it
3. CReject the sample as a probable wrong patient
4. DHold the result until a new sample is drawn
Answer and explanation in LearnFree account
Question 7 · Hard
For creatinine, the analytical CV is 3% and the within-subject biological CV is 4%. Using RCV = 2.77 × √(CVa² + CVi²), the smallest change between two results that is significant at the 95% level is:
1. AAbout 19%
2. BAbout 10%
3. CAbout 5%
4. DAbout 14%
Answer and explanation in LearnFree account
Question 8 · Hard
A hemodialysis patient's results two days ago and today: urea 24.6 and 4.1 mmol/L; creatinine 780 and 72 µmol/L (8.8 and 0.8 mg/dL); potassium 5.6 and 4.0 mmol/L; hemoglobin 98 and 139 g/L. He has had no dialysis or transfusion since. The best action is to:
1. ARerun the same tube and release it if the results agree
2. BRelease the results, since dialysis lowers urea and creatinine
3. CRelease the potassium only and hold the other results
4. DHold the results and request a new, positively identified sample
Answer and explanation in LearnFree account
Question 9 · Easy
A critical (panic) value is best defined as a result that:
1. AMay mean an immediate threat to the patient's life
2. BDiffers greatly from the patient's previous result
3. CFalls outside the laboratory's reference interval
4. DIs above the upper limit of the measuring range
Answer and explanation in LearnFree account
Question 10 · Medium
A potassium of 7.0 mmol/L is a critical value. What is the correct action?
1. ACheck validity, then phone the clinician with read-back
2. BRepeat it three times the next morning before reporting it
3. CEmail the report to the ward and mark it urgent
4. DRelease it with the routine report at the usual time
Answer and explanation in LearnFree account

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Errors, delta checks and critical value reporting

A potassium of 6.9 mmol/L was released and phoned to a ward as critical. An hour later, the technologist notices that the sample's hemolysis index was high, which should have stopped the result. What is the correct action?

Which of these errors occurs in the post-analytical phase of testing?

After an EQA failure, a laboratory finds that 40 vitamin D results reported last week were about 25% low, because a wrong calibrator value had been entered. The samples are stored frozen. What is the most appropriate action?

A technologist phones a critical sodium of 116 mmol/L. The nurse reads back the result correctly, but the medical record number she reads from the chart differs from the one on the request. The technologist should:

A delta check flags a patient's hemoglobin: 68 g/L (6.8 g/dL) yesterday, 92 g/L (9.2 g/dL) today. The record shows two units of red cells were transfused overnight, and the red cell indices are unchanged. What should the technologist do?

For creatinine, the analytical CV is 3% and the within-subject biological CV is 4%. Using RCV = 2.77 × √(CVa² + CVi²), the smallest change between two results that is significant at the 95% level is:

A hemodialysis patient's results two days ago and today: urea 24.6 and 4.1 mmol/L; creatinine 780 and 72 µmol/L (8.8 and 0.8 mg/dL); potassium 5.6 and 4.0 mmol/L; hemoglobin 98 and 139 g/L. He has had no dialysis or transfusion since. The best action is to:

A critical (panic) value is best defined as a result that:

A potassium of 7.0 mmol/L is a critical value. What is the correct action?