AACC AACC Specimen Collection & Processing 3

Question 1

What is the purpose of the serum separator tube (SST) gel in a gold or tiger-top tube?

Accepted Answer

To form a physical barrier between the clot and serum after centrifugation

Answer

To prevent hemolysis during centrifugation

Answer

To activate clotting faster than a plain red-top tube

Answer

To chelate metal ions that interfere with chemistry assays

Question 2

When performing a 24-hour urine collection for creatinine clearance, what instruction is most critical for the patient?

Accepted Answer

Discard the first morning void, then collect all urine for the next 24 hours, ending with the next day's first void

Answer

Collect only the first and last voids of the day

Answer

Refrigerate urine only during nighttime collection hours

Answer

Avoid drinking water during the collection period

Question 3

What is the clinical significance of detecting bilirubin crystals (bilirubin precipitate) in a urine sample?

Accepted Answer

Suggests hepatobiliary disease, as conjugated bilirubin is filtered by the kidneys only when elevated in plasma

Answer

Indicates urinary tract infection

Answer

Is a normal finding in concentrated morning urine

Answer

Indicates renal tubular acidosis

Question 4

What is the preferred collection container and preservative for a urine specimen tested for catecholamines (epinephrine, norepinephrine)?

Accepted Answer

Acidified collection jug (6N HCl preservative), kept cold

Answer

Plain sterile cup, no preservative, refrigerated

Answer

Boric acid preservative cup at room temperature

Answer

Sodium fluoride preserved cup for glycolysis inhibition

Question 5

According to CLSI standards, what is the maximum recommended time between venipuncture and centrifugation for a serum tube?

Accepted Answer

30 minutes to 1 hour after complete clotting

Answer

5 minutes

Answer

2 hours

Answer

4 hours at room temperature

Question 6

Which factor most significantly affects the stability of coagulation factors in plasma intended for PT/aPTT testing?

Accepted Answer

Temperature — factors degrade faster at room temperature than when refrigerated or frozen

Answer

Exposure to bright light during transport

Answer

Use of lithium heparin instead of sodium citrate

Answer

Delay in adding the activating reagent during testing