AACC AACC Specimen Collection & Processing 2

Question 1

What is the primary reason for inverting blood collection tubes gently after venipuncture?

Accepted Answer

To mix the additive thoroughly with the blood sample

Answer

To activate clotting factors in serum tubes

Answer

To prevent air bubble formation in the tube

Answer

To settle red cells to the bottom before centrifugation

Question 2

Which specimen type is required for coagulation testing (PT/INR, aPTT), and what is the critical blood-to-anticoagulant ratio?

Accepted Answer

Plasma from a light blue (sodium citrate) tube; 9:1 blood-to-anticoagulant ratio

Answer

Serum in a red-top tube; no specific ratio required

Answer

Whole blood in an EDTA tube; 5:1 ratio

Answer

Plasma from a green (heparin) tube; 4:1 ratio

Question 3

What is the recommended storage condition for most routine chemistry specimens (serum/plasma) if testing is delayed beyond 8 hours?

Accepted Answer

Refrigeration at 2–8°C after separating from cells

Answer

Room temperature in the original tube

Answer

Frozen at –20°C immediately after collection

Answer

Stored at 37°C to prevent protein denaturation

Question 4

What does the term 'hemolysis index' refer to in automated chemistry analyzers?

Accepted Answer

A spectrophotometric measurement of free hemoglobin used to flag and quantify hemolysis

Answer

A calculation of the hemoglobin A1c percentage

Answer

A ratio of red cell volume to plasma volume

Answer

A QC parameter for flagging analyzer errors

Question 5

For ammonia testing, which pre-analytical handling requirement is most critical?

Accepted Answer

Immediate chilling on ice and rapid transport to the laboratory

Answer

Warming the specimen to 37°C before transport

Answer

Collecting in a sodium fluoride tube to inhibit metabolism

Answer

Exposing the sample to room air to stabilize pH

Question 6

Which specimen is the gold standard for measuring true ionized calcium in critically ill patients?

Accepted Answer

Whole blood collected anaerobically in a heparinized syringe analyzed immediately

Answer

Serum collected in a red-top tube and spun at room temperature

Answer

Plasma from an EDTA tube after refrigeration

Answer

Urine from a 24-hour collection with HCl preservative