Which vacutainer tube should be used for apolipoprotein testing?

Apolipoprotein Testing: Serum or Plasma Collection

For apolipoprotein testing (ApoB, ApoA1), use either serum separator tubes (SST/gold top) or EDTA plasma tubes (lavender top). Both specimen types provide clinically equivalent results for apolipoprotein measurement, with the key advantage being that fasting is not required for apolipoprotein testing 1, 2, 3.

Recommended Tube Types

Primary Options:

• Serum Separator Tubes (SST): Gold or tiger top tubes with gel separator 4

  • Allow 30-60 minutes clotting time at room temperature
  • Centrifuge at 1500-2000 × g for 10 minutes at 4°C

• EDTA Plasma Tubes: Lavender top tubes 5, 4, 5

  • Invert 8-10 times immediately after collection
  • Centrifuge within 2 hours at 1500-2000 × g for 10 minutes at 4°C
  • EDTA is versatile and suitable for multiple downstream analyses

Critical Collection Procedures:

For Serum Collection 4:

• Invert tubes 5 times immediately after blood draw (except glass red top tubes)
• Allow clotting for 30-60 minutes upright at room temperature
• If not centrifuging immediately, refrigerate at 4°C for no longer than 2 hours
• Transfer serum to intermediary tube before aliquoting to ensure homogeneity

For Plasma Collection 4:

• Invert EDTA tubes 8-10 times immediately after collection
• Store at 4°C before centrifugation (preferable to room temperature)
• Centrifuge within 2 hours of collection
• Avoid disturbing the buffy coat layer when transferring plasma

Blood Draw Order

When collecting multiple tube types in a single venipuncture, follow this standardized sequence to prevent cross-contamination 4:

1. Blood culture tubes
2. Sodium citrate tubes
3. Serum tubes (for apolipoproteins)
4. Heparin tubes
5. EDTA tubes (for apolipoproteins)
6. Sodium fluoride/potassium oxalate tubes

Key Advantages of Each Tube Type

Serum tubes provide excellent stability and are standard for many lipid measurements 6, 7. Research demonstrates that SST tubes with gel separators minimize cellular contamination and hemolysis 5.

EDTA plasma tubes offer practical advantages: they're inexpensive, readily available in clinical labs, and suitable for a wide range of analyses including genomics, proteomics, and metabolomics 5. EDTA is less likely to interfere with analyte detection compared to other anticoagulants 5.

Critical Pitfalls to Avoid

• Hemolysis: Inspect samples for hemolysis, which significantly deteriorates sample quality 4. Use a hemolysis reference chart to document quality.
• Tube filling: Fill tubes to the manufacturer's recommended volume to maintain proper blood-to-additive ratios 4
• Mixing: Failure to properly invert tubes immediately after collection can result in microclots that obstruct analytical instruments 4
• Storage delay: Prolonged pre-centrifugation delay degrades biomarkers; centrifuge within 2 hours or refrigerate (not exceeding 24 hours) 4

Standardization Considerations

Apolipoprotein assays should use calibration traceable to WHO/IFCC reference materials 1, 3. The IFCC is establishing liquid chromatography-tandem mass spectrometry reference procedures for ApoB to ensure traceability to SI units (g/L) 1, 3. Until this transition is complete, laboratories should state the assay method used on reports due to lack of complete standardization 1.