Specimen Collection and Pre-Analytical Processing Flashcards

Leaving a tourniquet on for more than 1 minute before drawing blood is most likely to falsely increase which result?

Answer: Total protein

Prolonged stasis concentrates large molecules and cells like proteins, so total protein rises.

A specimen for serum cortisol is ordered to assess the normal diurnal peak. When should it be collected?

Answer: Early morning, around 8 AM

Cortisol peaks in the early morning and is lowest near midnight.

Which specimen should be protected from light during transport?

Answer: Neonatal bilirubin

Bilirubin breaks down when exposed to light, which falsely lowers results.

A 24-hour urine collection begins at 7:00 AM. How should the first void at 7:00 AM be handled?

Answer: Discard it and then collect all urine through 7:00 AM the next day

The first void is discarded because it was formed before the timed period began, while the final void at 7:00 AM next day is kept.

A heparinized whole-blood specimen cannot be tested right away. Which test would be least affected by a short delay?

Answer: Plasma sodium

Sodium is stable, while ammonia and lactate rise in vitro and ionized calcium shifts with pH changes when the tube is open.

Which statement correctly describes how serum differs from plasma?

Answer: Serum lacks fibrinogen and other clotting factors used in clot formation

Serum is the fluid left after clotting, so fibrinogen has been used up, while plasma still contains it.

A specimen tube carries the patient's full name and date of birth, but no collection date/time or collector ID. What should the lab do?

Answer: Follow lab policy: reject it or hold for documented correction, as the label is incomplete

Required label elements include collection time and collector ID, and undocumented label changes are not allowed.