The Development of a Standardized Quality Assessment Material to Support Xpert HIV-1 Viral Load Testing for ART Monitoring in South Africa

The tiered laboratory framework for HIV viral load monitoring accommodates a range of HIV viral load testing platforms, with quality assessment critical to ensure quality patient testing. HIV plasma viral load testing is challenged by the instability of viral RNA. An approach using an RNA stabilizing buffer is described for the Xpert HIV-1 Viral Load (Cepheid) assay and was tested in remote laboratories in South Africa. EDTA-plasma panels with known HIV viral titres was prepared in PrimeStore molecular transport medium for per-module verification and per-instrument external quality assessment. The panels were transported at ambient temperature to 13 testing laboratories during 2017-2018, tested according to standard procedures and uploaded to a web portal for analysis A total of 275 quality assessment specimens (57 verification panels and two EQA cycles) were tested. All participants passed verification (n=171 specimens) with an overall concordance correlation (ρc) of 0.997 (95%confidence interval [CI]:0.996,0.998) and a mean log bias of -0.019log cp/mL (95%CI:-0.044,0.063). The overall EQA ρc (n=104 specimens) was 0.999 (95%CI:0.998,0.999), with a mean log bias of 0.03 log cp/mL 95%(CI:0.02,0.05). The panels are suitable for use in quality monitoring of Xpert HIV-1 VL and are applicable to laboratories in remote settings.