A point-of-care triage test for HIV virological failure: filling the gaps in viral load coverage

Title

A point-of-care triage test for HIV virological failure: filling the gaps in viral load coverage

Presenter

Anna Saura-LÃ¡zaro

Authors

A. Saura-Lázaro * (1), P. Bock (2), E. van den Bogaart (3), J. van Vliet (3), L. Granés (4), K. Nel (2), V. Naidoo (2), Y. Saunders (2), M. Scheepers (2), R. Paulussen (3), D. Naniche (1), E. López-Varela (1,2)

Institutions

(1) Barcelona Centre for International Health Research (CRESIB), Hospital Clinic-Universidad de Barcelona, Barcelona, Spain, (2) Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa, (3) Mondial Diagnostics, Amsterdam, Netherlands, the, (4) Hospital Clínic de Barcelona, Barcelona, Spain

BACKGROUND: Viral load (VL) monitoring in antiretroviral treatment (ART) patients is challenging, especially in high-burden settings. Access to an accurate, affordable point-of-care test (POCT) could greatly enhance ART outcomes.IFN-É£-induced protein 10 (IP-10) is a chemokine strongly correlated with human immunodeficiency virus (HIV) VL that could serve to predict virological failure (VF) and to triage patients requiring VL testing. This study aimed to evaluate the field performance of a semi-quantitative prototype lateral flow IP-10 POCT as a screening test for VF in South Africa.
METHODS: Finger prick capillary blood was collected from patients attending a primary health clinic in the Western Cape for direct application by trained nurses onto the IP-10 POCT (index test) and compared with a plasma VL result taken '¤1 month prior (reference test) amongst adult patients on ART for '¥ 1 year. Logistic regression with penalized likelihood was used to build an IP-10 POCT reading values-based model able to identify individuals with VF (VL > 1,000 copies/mL). The area under the receiver operating characteristic curves (AUC) was calculated to evaluate model prediction. Testing cost saving was estimated assuming a unit cost of 2 USD for IP-10 POCT, 22 USD for VL test plus 60% of test-associated costs.
RESULTS: Among the 209 participants (median age 38 years and 88% female), 18% had VF. Median IP-10 POCT reading values were higher among individuals with VF compared to those without (24.0 vs. 14.6; p < 0.001). The IP-10 POCT predicted VF with an AUC = 0.76 (95% confidence interval (CI), 0.67'0.85). The model identified VF with 91.9% sensitivity (95% CI, 78.1%'98.3%) and 35.1% specificity (28.0%'42.7%). Projecting a VF prevalence of 18% in a simulated cohort of 1,000 ART patients, an IP-10 screening POCT would avert > 30% of the routine VL monitoring tests and associated costs.
CONCLUSIONS: The IP-10 POCT is an effective triage test for routine VL monitoring. Combining a highly sensitive, low-cost IP-10 POCT-based screening with VL testing in a two-step decision algorithm could provide a greatly needed monitoring tool in settings with low VL coverage, and result in significant savings for health systems.

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