MLS Diagnostic Procedures & Reporting 2 — Questions and Answers
Question 1: A critical value for serum potassium is reported to the nurse. The nurse is unavailable. What is the correct next step?
- Leave a voicemail and document the attempt
- Contact the charge nurse or covering physician and document (Correct answer)
- Wait 30 minutes and call again
- File the result and let the physician see it on rounds
Correct answer: Contact the charge nurse or covering physician and document
Critical values must be communicated to a responsible caregiver immediately; if the primary nurse is unavailable, the charge nurse or covering provider must be notified and all attempts documented.
Question 2: Which analyte requires a timed 24-hour urine collection for the most clinically meaningful result?
- Urine glucose
- Creatinine clearance (Correct answer)
- Urine specific gravity
- Urine pH
Correct answer: Creatinine clearance
Creatinine clearance requires a 24-hour urine collection to calculate glomerular filtration rate accurately by accounting for diurnal variation in excretion.
Question 3: A laboratory receives a blood culture bottle that has been incubating for 5 days with no growth signal. What is the standard reporting outcome?
- Report 'No growth at 72 hours'
- Report 'No growth at 5 days' and discard (Correct answer)
- Sub-culture to solid media and incubate another 5 days
- Perform Gram stain immediately
Correct answer: Report 'No growth at 5 days' and discard
Standard blood culture incubation is 5 days; bottles with no instrument signal at that point are reported as 'No growth at 5 days' and discarded per protocol.
Question 4: Which of the following urine findings is most consistent with nephrotic syndrome?
- 3+ proteinuria with fatty casts and oval fat bodies (Correct answer)
- WBC casts with bacteriuria
- RBC casts with hematuria
- Waxy casts with granular casts only
Correct answer: 3+ proteinuria with fatty casts and oval fat bodies
Nephrotic syndrome is characterized by massive proteinuria, hypoalbuminemia, and lipiduria, producing fatty casts and oval fat bodies (Maltese cross pattern) on urinalysis.
Question 5: A hemoglobin electrophoresis at alkaline pH shows a band migrating to the S position. Which confirmatory test best differentiates HbS from HbD?
- Acid electrophoresis (pH 6.2) (Correct answer)
- Osmotic fragility test
- Heinz body preparation
- Reticulocyte count
Correct answer: Acid electrophoresis (pH 6.2)
Acid electrophoresis separates HbS from HbD because HbD migrates with HbA at acid pH while HbS remains in the S position, confirming the identity of the variant.
Question 6: A CSF specimen is received with xanthochromia. This finding is most suggestive of:
- Bacterial meningitis
- Subarachnoid hemorrhage that occurred hours to days ago (Correct answer)
- Traumatic tap
- Viral encephalitis
Correct answer: Subarachnoid hemorrhage that occurred hours to days ago
Xanthochromia (yellow discoloration) results from oxyhemoglobin and bilirubin released after red cell lysis and is a hallmark of subarachnoid hemorrhage, typically appearing 2–4 hours after the bleed.
Question 7: When reporting a Pap smear result using the Bethesda System, the term 'NILM' indicates:
- No squamous cells present
- Negative for intraepithelial lesion or malignancy (Correct answer)
- Needs immediate liquid-based cytology repeat
- Non-invasive low-grade malignancy
Correct answer: Negative for intraepithelial lesion or malignancy
NILM stands for Negative for Intraepithelial Lesion or Malignancy, meaning the cervical sample shows no cytologic evidence of a precancerous or cancerous process.
MLS Diagnostic Procedures & Reporting 2
A critical value for serum potassium is reported to the nurse.
The nurse is unavailable.
What is the correct next step?