AACC Specimen Collection & Processing Flashcards
6 cards from real AACC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 AACC Specimen Collection & Processing flashcards as text
What is the purpose of the serum separator tube (SST) gel in a gold or tiger-top tube?
Answer: To form a physical barrier between the clot and serum after centrifugation
The thixotropic gel in SST tubes migrates during centrifugation to form a stable barrier between the clot and serum, preventing analyte exchange and enabling easy serum harvest.
When performing a 24-hour urine collection for creatinine clearance, what instruction is most critical for the patient?
Answer: Discard the first morning void, then collect all urine for the next 24 hours, ending with the next day's first void
Proper 24-hour collection begins by discarding the first morning void (to establish a clean start point) and ends with collecting the void exactly 24 hours later.
What is the clinical significance of detecting bilirubin crystals (bilirubin precipitate) in a urine sample?
Answer: Suggests hepatobiliary disease, as conjugated bilirubin is filtered by the kidneys only when elevated in plasma
Conjugated (direct) bilirubin is water-soluble and filtered by the glomerulus when plasma levels are elevated, indicating liver disease, biliary obstruction, or hepatitis.
What is the preferred collection container and preservative for a urine specimen tested for catecholamines (epinephrine, norepinephrine)?
Answer: Acidified collection jug (6N HCl preservative), kept cold
Catecholamines are unstable in alkaline or neutral pH; acidifying urine to pH <3 with HCl preserves them from oxidative degradation throughout the 24-hour collection.
According to CLSI standards, what is the maximum recommended time between venipuncture and centrifugation for a serum tube?
Answer: 30 minutes to 1 hour after complete clotting
CLSI recommends centrifugation within 30–60 minutes of collection after complete clot formation to minimize analyte degradation and cellular metabolism effects.
Which factor most significantly affects the stability of coagulation factors in plasma intended for PT/aPTT testing?
Answer: Temperature — factors degrade faster at room temperature than when refrigerated or frozen
Labile coagulation factors (especially Factor V and VIII) degrade rapidly at room temperature; plasma for coagulation studies must be tested within 4 hours or frozen at –20°C.