Specimen Collection & Handling Flashcards

What is a common specimen-handling cause of false-positive PCR results?

Answer: Cross-contamination from aerosols or amplicon carryover

Tiny amounts of contaminating nucleic acid can be amplified, producing false positives.

In a unidirectional PCR workflow, where should incoming patient specimens be opened and processed?

Answer: In the pre-amplification specimen processing area

Specimens must stay in pre-amplification areas to avoid exposure to amplified products.

Which situation is a standard reason to reject a specimen for PCR testing?

Answer: Specimen container is unlabeled

Unlabeled specimens cannot be positively identified and must be rejected.

Why can prolonged formalin fixation of tissue compromise PCR results?

Answer: Formalin causes cross-linking and fragmentation of nucleic acids

Extended fixation creates protein-nucleic acid cross-links and breaks DNA/RNA into short fragments.

Which tissue fixative is least suitable for subsequent PCR analysis?

Answer: Bouin's solution

Bouin's contains picric acid, which severely degrades nucleic acids.

Which collection tube is designed to stabilize intracellular RNA in whole blood at collection?

Answer: PAXgene Blood RNA tube

PAXgene tubes contain a reagent that immediately stabilizes RNA and prevents changes in gene expression.

For HIV-1 viral load testing, how soon is plasma typically separated from cells after EDTA blood collection?

Answer: Within 6 hours

Most assay inserts require plasma separation within about 6 hours to preserve viral RNA.