Certified Medical Assistant (CMA AAMA)Procedures, Examinations and DiagnosticsHard
A medical assistant draws a blood specimen and notices the sample appears pink-tinged in the serum after centrifugation. Which technique error during the draw most likely caused this result?
- AVigorously shaking the tube immediately after collection
- BApplying the tourniquet for less than 30 seconds
- CUsing a 21-gauge needle for the venipuncture
- DAllowing the tube to fill completely with correct additive ratio
Show answer & explanationAnswer & explanation
Correct answer: A. Vigorously shaking the tube immediately after collection
Vigorous shaking of a blood tube causes mechanical trauma to red blood cells, releasing hemoglobin into the plasma or serum and producing a pink or red-tinged appearance known as hemolysis, which can invalidate many chemistry results.
Why the other options are wrong
- B. A short tourniquet time is appropriate and does not cause hemolysis.
- C. A 21-gauge needle is standard size and does not typically cause hemolysis when used properly.
- D. Correct fill volume and additive ratio prevents problems; it does not cause hemolysis.
Hemolysis Causes
Hemolysis is the rupture of red blood cells releasing hemoglobin into serum/plasma, most often caused by improper technique such as vigorous mixing, small-gauge needles, or forcing blood through a needle.
- Causes include vigorous shaking, too-small needle gauge, wet alcohol at site
- Hemolysis affects potassium, LDH, and other chemistry results
- Gently invert tubes with additive per manufacturer instructions, never shake
Memory trick: 'Shake it and break it'—rough handling bursts red cells.