Specimen Collection and Pre-Analytical Processing Flashcards

During a capillary heel puncture on a newborn, where should the puncture be made?

Answer: Medial or lateral plantar surface of the heel

The medial or lateral plantar surfaces avoid the calcaneus and reduce the risk of osteomyelitis.

Why is the first drop of blood wiped away during a capillary puncture?

Answer: It may contain excess tissue fluid and residual alcohol

The first drop is diluted with tissue fluid and may contain alcohol, which can cause hemolysis or dilution.

A cerebrospinal fluid collection yields four numbered tubes. Tube 3 is usually sent to which department?

Answer: Hematology for cell counts

Tube 3 is the least likely to have traumatic-tap blood, so it is best for cell counts.

Which disinfectant is preferred for skin preparation when collecting blood cultures in adults?

Answer: Chlorhexidine gluconate

Chlorhexidine (often in alcohol) gives superior, longer-lasting skin antisepsis and lowers contamination rates.

When collecting blood cultures by syringe, which bottle should be inoculated first?

Answer: Anaerobic bottle

With a syringe, the anaerobic bottle goes first so air in the syringe does not enter it.

For an arterial blood gas specimen that cannot be analyzed within 30 minutes, which handling is currently recommended for a plastic syringe?

Answer: Keep at room temperature and analyze as soon as possible

Plastic syringes are kept at room temperature because chilling lets oxygen diffuse through the plastic.

What is the main purpose of the modified Allen test before a radial artery puncture?

Answer: Confirm adequate collateral circulation from the ulnar artery

The Allen test confirms the ulnar artery can perfuse the hand if the radial artery is damaged.