Domain 7.5Phlebotomy
Specimen Processing
Last updated June 16, 2026
Overview
Specimen processing covers the preanalytical phase after the tube is filled. Proper handling prevents errors like hemolysis and degradation. As a medical assistant, you are the guardian of specimen integrity.
1. Post-Collection Handling
A. Verify Labeling
Ensure tubes were labeled at the patient's side (as detailed in the Procedure section). The label must contain: Patient Name, DOB, Date, Time, and Your Initials.
B. Proper Mixing
- Technique: Gentle inversion 8-10 times.
- Avoid: Vigorously shaking the tube. This is a primary cause of hemolysis.
C. Common Preanalytical Errors (Review)
| Error | Definition | Cause | Appearance |
|---|---|---|---|
| Hemolysis | Rupture of RBCs. | Shaking tubes; small needle; milking finger; wet alcohol. | Serum/plasma appears pink or red. |
| Hemoconcentration | Concentration of cells/solutes. | Tourniquet on > 1 minute. | No visible change; falsely elevated results. |
2. Processing Techniques
A. Centrifugation
Separates components by density.
- Serum: Allow Red/SST tubes to clot fully (30-60 mins) before spinning.
- Plasma: Green/Blue tubes can be spun immediately.
- Balance: Always place tubes of equal volume opposite each other. Unbalanced centrifuges are dangerous.
B. Aliquoting
Transferring serum/plasma to a secondary tube.
- Tool: Use a disposable pipette.
- Safety: Never pour; never use a needle/syringe to transfer.
3. Special Handling Requirements
Some tests are sensitive to the environment and require specific actions immediately after the draw.
| Requirement | Reason | Key Examples |
|---|---|---|
| Protect from LIGHT | Light breaks down the analyte. Wrap in foil or use amber tube. | Bilirubin, Vitamin B12, Folate. |
| Chilled (Ice Slurry) | Slows metabolic activity. | Arterial Blood Gas (ABG), Ammonia, Lactic Acid. |
| Keep WARM (37°C) | Prevents clumping (agglutination). | Cold Agglutinins. |
| Timed: Trough Level | Measures lowest drug level. | Draw 30 mins BEFORE next dose. |
4. Final Key Takeaways
- Handling: Invert gently; never shake.
- Centrifuge: Balance the tubes. Let serum clot first.
- Light Sensitive: Bilirubin (wrap in foil).
- Chilled: ABG, Ammonia (ice slurry).
- Warm: Cold Agglutinins.
- Trough Level: Draw right before the next dose.