Change to Purple Top Tubes for HIV Viral Load Testing
Effective immediately, blood specimens for HIV viral load testing should be collected in EDTA (purple top) tubes instead of ACD-A (yellow top) tubes.
A change in the specimen preparation method has been implemented by the laboratory to improve the consistency of results for HIV viral load testing and decrease the test failure rate. FDA approved labeling of the new specimen preparation method requires the use of EDTA (purple top) tubes.
The actual method of HIV viral load testing has not changed. However, results from EDTA tubes may be up to 15% higher than results from ACD-A tubes because of the 1.5 milliliter dilution volume of the ADC-A anticoagulant.
For questions, please contact Aaron Bossler, M.D., Ph.D., Molecular Pathology Laboratory Interim Director, at 4-9566.