Point-of-care HIV viral load assays to simplify care

31 August 2016

CAPRISA’s Laboratory technician, Mr Keenan Govender, Enrolled Nurse, Ms Mandisa Msomi and Dr Nigel Garrett, demonstrating how to per-form the Xpert® HIV-1 VL assay

In line with World Health Organisa-tion recommendations and the UNAIDS 90-90-90 target, the South Af-rican Department of Health announced the implementation of the universal test and treat strategy for HIV positive pa-tients from 1 September 2016. While ART coverage will rapidly expand to reach the more than 6 million people living with HIV in South Africa, successful lifelong therapy requires routine HIV viral load (VL) monitoring to ensure treatment adherence and control of drug resistance. Simpler, patient-centered and more cost-effective models of care are urgently required that focus on maintaining viral suppression, improve retention in care, and reduce the burden on HIV care providers and laboratories.


In this study, Garrett et al report on their early clinical experience evaluating the point-of-care Xpert® HIV-1 VL assay, which is processed on the GeneXpert® System (Cepheid, Sunnydale, California, USA) against the gold-standard Roche Taqman version 2 assay (Roche Diagnostics, Switzerland). The Xpert® HIV-1 VL is a fully automated real-time molecular cartridge-based assay with a linear range of 40 to 10 million copies/ml of HIV RNA, and can be run in a clinical setting providing a result within 90 minutes.

Investigating samples from 42 women participating in the CAPRISA 002 Acute Infection Study, Xpert® HIV-1 VL correlated strongly with the Taqman assay across the VL spectrum (Spearman ?=0.94, p<0.001, Figure 1). A Bland-Altman plot showed a mean difference between Taqman and Xpert® results of -0.10 log copies/ml (95% limits of agreement -0.59 to 0.39) with slightly higher values on Xpert®. Importantly, only one woman was misclassified using a VL threshold of 1000 copies/ml, the current threshold to trigger adherence counselling and treatment switches. This woman had a Taqman result of 1302 copies/ml and a Xpert® HIV-1 VL result of 792 copies/ml.

This first clinic-based validation provides some early evidence that point-of-care VL assays may be able to fill an important gap in the rapid scale–up of ART globally. Supported by funding from the National institute of Health, US, the authors will next implement a chronic HIV care model that includes Xpert® HIV-1 VL testing and task-shifting from professional to enrolled nurses.

Figure 1. Cor-relation be-tween Xpert® HIV-1 viral load and Roche Taq-man version 2 assays

 

 

For further reading see:
Garrett NJ, et al. Diagnostic accuracy of the point-of-care xpert HIV-1 viral load assay in a South African HIV Clinic. JAIDS 2016; 72(2):e45-48.