Specimen Collection & Processing Flashcards

What is the primary purpose of centrifugation in blood specimen processing?

Answer: To separate cellular components from plasma or serum for testing

Centrifugation uses centrifugal force to separate heavier cellular elements (red and white blood cells, platelets) from the liquid portion (plasma or serum), which contains the analytes to be measured.

Which specimen type requires protection from light during collection and transport to the laboratory?

Answer: Bilirubin and porphyrins

Bilirubin and porphyrins are photosensitive compounds that degrade when exposed to light; tubes must be wrapped in foil or placed in amber containers immediately after collection.

What does the abbreviation SST stand for in the context of laboratory specimen collection?

Answer: Serum Separator Tube

SST stands for Serum Separator Tube; it contains a clot activator and an inert gel that migrates between the serum and clot during centrifugation, providing a physical barrier that preserves specimen integrity.

When performing a capillary (fingerstick) blood collection, which part of the finger is the preferred puncture site?

Answer: The center pad of the middle or ring finger, slightly to one side

The fleshy pad slightly to one side of the center of the middle or ring finger is preferred because it has adequate tissue depth, good blood flow, and avoids the bone and nerves located at the very tip and sides.

What is the maximum acceptable time limit for processing most blood specimens (centrifuging serum or plasma) after collection?

Answer: 2 hours

Most specimens should be centrifuged and the serum or plasma separated from cells within 2 hours of collection to prevent analyte degradation and cellular metabolism from altering test results.

Which anticoagulant mechanism in EDTA (lavender) tubes prevents blood from clotting?

Answer: Chelating (binding) calcium ions needed for the coagulation cascade

EDTA works by chelating divalent calcium ions (Ca²⁺), which are essential cofactors in multiple steps of the coagulation cascade; without calcium, clotting cannot proceed.

If a blood specimen appears visibly lipemic (milky white), what should the laboratory assistant do?

Answer: Document the lipemia, notify the laboratory supervisor, and note it may interfere with certain assays

Lipemia (elevated triglycerides causing turbidity) can interfere with photometric and turbidimetric assays; the lab assistant must document the finding, flag the specimen, and inform the supervisor so interference can be assessed and corrective action taken.