This study was conducted in 2 parts: Firstly, fresh random samples (n = 75) were tested at four time intervals (0, 24, 36 and 48 h) post-venesection to review reproducibility of CD38 MFI expression. Secondly, the CD38 MFI assay was introduced into a pilot regional testing facility and random samples (n = 40) were validated against values obtained on matched samples tested at the reference laboratory.
The CD38 assay showed acceptable accuracy and reproducibility up to 36 h (98%similarity) after venesection with some reduction in CD38 MFI to 94%at 48 h (bias < 0.2MFI,%CV < 5).
Implementation at the secondary testing site was successful with 98%similarity (%SIM CV < 5%) compared to the reference laboratory.
The assay proved stable over time and could be tested until 48 h after venesection with no loss of CD38 MFI. Off-site implementation also proved successful, as such, the CD38 assay offers a reliable real time supplementary test to long-term VL monitoring of HIV infected patients on the national ART programme.