Capillary and Special Collections Flashcards

When performing a capillary puncture on a newborn for a metabolic screening, which of the following actions is a critical step to ensure a valid specimen?

Answer: Applying a single, large drop of blood to completely saturate each circle on the filter paper.

For newborn metabolic screening, it is crucial to allow a large drop of blood to form and then touch the filter paper to the drop, allowing it to soak through and completely fill the circle in a single application. Layering multiple drops or 'milking' the finger can cause inaccurate results. Wiping away the first drop is standard to remove tissue fluid, puncturing the back of the heel risks bone injury, and excessive pressure can cause hemolysis and contamination with tissue fluids.

A phlebotomist needs to collect a capillary blood specimen for a complete blood count (CBC), a serum chemistry test, and a blood smear. According to CLSI guidelines, what is the correct order of draw for these microcollection tubes?

Answer: EDTA (lavender), Blood smear, Serum (red/gold)

The CLSI-recommended order of draw for capillary collections prioritizes specimens that are most affected by clotting. EDTA tubes (for hematology tests like CBC) are collected first to prevent platelet aggregation and microclot formation. Blood smears would be made next from the EDTA tube or directly from the second drop of blood. Other additive tubes follow, and serum tubes (which need to clot) are collected last.

When collecting a blood sample for a legal blood alcohol content (BAC) test, which of the following is the most appropriate cleansing agent to use for site preparation?

Answer: Non-alcohol based antiseptic, such as benzalkonium chloride

Using an alcohol-based cleanser, including isopropyl alcohol or iodine preparations containing alcohol, can falsely elevate the blood alcohol level in the test results. Therefore, a non-alcohol based antiseptic such as benzalkonium chloride, povidone-iodine (if confirmed non-alcoholic), or green surgical soap must be used for this special collection.

A phlebotomist is performing a heel stick on an infant. To avoid the risk of osteomyelitis, the puncture should be made on which part of the heel?

Answer: The medial or lateral plantar surface of the heel

The safest areas for a heel puncture are the medial and lateral portions of the plantar (bottom) surface. Puncturing the posterior curvature or the central arch area risks injuring the calcaneus (heel bone), which can lead to a serious bone infection called osteomyelitis. Previously punctured sites should be avoided to prevent infection.

During a blood culture collection using a butterfly needle and an evacuated tube system, a phlebotomist must fill both an aerobic and an anaerobic bottle. Which bottle should be filled first and why?

Answer: The aerobic bottle, to ensure any air in the butterfly tubing is drawn into it.

When using a butterfly (winged infusion set) for blood culture collection, the aerobic bottle must be inoculated first. The tubing of the butterfly set contains air, and if the anaerobic bottle is filled first, this air will be drawn into the bottle, destroying the anaerobic environment required for the growth of anaerobic bacteria.

Which of the following is a key requirement for a specimen collected for legal or forensic purposes, such as paternity testing or a legal drug screen?

Answer: A complete chain-of-custody form must be maintained.

A chain-of-custody is a legal document that provides a chronological record of the specimen's handling, from collection to disposal. For any test with legal implications, maintaining a strict and unbroken chain-of-custody is the most critical requirement to ensure the specimen's integrity and admissibility in court.