CMLA Specimen Collection & Processing 2 — Questions and Answers
Question 1: Which type of specimen typically requires transport on ice to preserve analyte integrity?
- Routine CBC lavender tube
- Ammonia, lactic acid, or arterial blood gas specimens (Correct answer)
- Urine dipstick specimens
- Standard coagulation light blue tubes
Correct answer: Ammonia, lactic acid, or arterial blood gas specimens
Ammonia, lactic acid, and arterial blood gases are labile analytes that continue to be metabolized by cells at room temperature; ice slows this process and preserves accurate results.
Question 2: What does hemolysis in a blood sample indicate, and which test result is most critically affected?
- Excess white blood cells; affects WBC count
- Rupture of red blood cells; most critically affects potassium levels (Correct answer)
- Clot formation; affects coagulation studies
- Bacterial contamination; affects blood culture results
Correct answer: Rupture of red blood cells; most critically affects potassium levels
Hemolysis releases intracellular contents (particularly potassium) from red blood cells into the serum, falsely elevating serum potassium and several other analytes.
Question 3: What is the correct antiseptic used to prepare the skin site before drawing blood cultures?
- 70% isopropyl alcohol alone
- Povidone-iodine or chlorhexidine gluconate scrub followed by 70% alcohol (Correct answer)
- Soap and water only
- Benzalkonium chloride wipe
Correct answer: Povidone-iodine or chlorhexidine gluconate scrub followed by 70% alcohol
Blood cultures require a two-step antiseptic preparation (povidone-iodine or chlorhexidine followed by alcohol) to reduce skin flora and minimize the risk of false-positive contamination.
Question 4: What is the proper handling procedure for a urine culture specimen once collected?
- Store at room temperature for up to 24 hours
- Refrigerate at 2–8°C and process within 2 hours, or within 24 hours if refrigerated (Correct answer)
- Freeze the specimen immediately at -20°C
- Add a preservative and store indefinitely
Correct answer: Refrigerate at 2–8°C and process within 2 hours, or within 24 hours if refrigerated
Urine culture specimens must be refrigerated at 2–8°C to inhibit bacterial overgrowth; they should be processed within 2 hours at room temperature or within 24 hours if refrigerated to ensure accurate colony counts.
Question 5: How many times should most anticoagulant blood tubes be gently inverted after collection, and why?
- 1–2 times, to prevent shaking the sample
- 8–10 times, to thoroughly mix the additive with blood (Correct answer)
- 20 or more times, to ensure full anticoagulation
- Inversion is unnecessary; tubes mix automatically in the vacutainer holder
Correct answer: 8–10 times, to thoroughly mix the additive with blood
Gentle inversion 8–10 times ensures the anticoagulant or additive is evenly distributed throughout the blood sample without causing hemolysis from vigorous shaking.
Question 6: What additive is found in gray top tubes, and what is it primarily used to test?
- Lithium heparin; lipid panels
- Sodium fluoride and potassium oxalate; glucose and blood alcohol levels (Correct answer)
- EDTA; complete blood count
- Sodium citrate; coagulation studies
Correct answer: Sodium fluoride and potassium oxalate; glucose and blood alcohol levels
Gray top tubes contain sodium fluoride (glycolytic inhibitor) and potassium oxalate (anticoagulant), which together inhibit glucose metabolism, making them the standard choice for fasting glucose and forensic blood alcohol testing.
Question 7: When collecting a 24-hour urine specimen, what should the patient do with the first morning void on day one?
- Collect it as the first specimen in the container
- Discard it and note the time, then collect all urine for the next 24 hours (Correct answer)
- Save it in a separate container and add it at the end
- Use it to calibrate the collection volume
Correct answer: Discard it and note the time, then collect all urine for the next 24 hours
The first morning void is discarded to establish a clean starting point (empty bladder at time zero); all urine produced over the next 24 hours, including the final void the following morning, is then collected.
CMLA Specimen Collection & Processing 2
Which type of specimen typically requires transport on ice to preserve analyte integrity?