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
Which tube additive is found in a lavender/purple-top tube used for hematology testing, and what is its mechanism of action?
Answer: EDTA — chelates calcium and magnesium to inhibit coagulation
EDTA (ethylenediaminetetraacetic acid) in lavender-top tubes chelates divalent cations required for the coagulation cascade, preserving cell morphology for CBC analysis.
What is the recommended order of draw when collecting multiple tubes by venipuncture, according to CLSI guidelines?
Answer: Blood cultures → light blue → red/SST → green → lavender → gray
The CLSI-recommended order of draw minimizes additive carryover: blood cultures first (sterility), then light blue (citrate), red/SST, green (heparin), lavender (EDTA), and gray (fluoride/oxalate).
What is the maximum acceptable time for a serum specimen to remain as a clot before centrifugation under standard pre-analytical conditions?
Answer: 15–30 minutes at room temperature
Serum tubes should be allowed to clot for 15–30 minutes at room temperature before centrifugation to ensure complete fibrin formation and prevent fibrin strands in the serum.
Which pre-analytical variable is most likely to cause falsely elevated serum potassium levels?
Answer: Hemolysis releasing intracellular potassium into the sample
Hemolysis releases potassium from erythrocytes into the serum, causing falsely elevated results because intracellular potassium concentration is approximately 20–30 times higher than plasma levels.
For glucose testing, why is a gray-top tube (sodium fluoride/potassium oxalate) preferred over a serum tube?
Answer: Sodium fluoride inhibits glycolysis, preserving glucose concentration
Sodium fluoride inhibits enolase, a glycolytic enzyme, halting glucose metabolism by red blood cells and stabilizing glucose levels for up to 24 hours.
When collecting a urine specimen for culture and sensitivity, which collection method is preferred to minimize contamination?
Answer: Midstream clean-catch in a sterile container
A midstream clean-catch specimen, collected after cleaning the urethral area and discarding the initial stream, minimizes contamination from periurethral flora.