Fourth generation point of care testing for HIV: validation in an HIV-positive population

Field accuracy of fourth-generation rapid diagnostic tests for acute HIV-1: a systematic review

INTRODUCTION

Fourth-generation HIV-1 rapid diagnostic tests (RDTs) detect HIV-1 p24 antigen to screen for acute HIV-1. However, diagnostic accuracy during clinical use may be suboptimal.

METHODS

Clinical sensitivity and specificity of fourth-generation RDTs for acute HIV-1 were collated from field evaluation studies in adults identified by a systematic literature search.

RESULTS

Four studies with 17 381 participants from Australia, Swaziland, the United Kingdom and Malawi were identified. All reported 0% sensitivity of the HIV-1 p24 component for acute HIV-1 diagnosis; 26 acute infections were missed. Specificity ranged from 98.3 to 99.9%.

CONCLUSION

Fourth-generation RDTs are currently unsuitable for the detection of acute HIV-1.

Multi-centre evaluation of the Determine HIV Combo assay when used for point of care testing in a high risk clinic-based population

Background

Determine HIV Combo (DHC) is the first point of care assay designed to increase sensitivity in early infection by detecting both HIV antibody and antigen. We conducted a large multi-centre evaluation of DHC performance in Sydney sexual health clinics.

Methods

We compared DHC performance (overall, by test component and in early infection) with conventional laboratory HIV serology (fourth generation screening immunoassay, supplementary HIV antibody, p24 antigen and Western blot tests) when testing gay and bisexual men attending four clinic sites. Early infection was defined as either acute or recent HIV infection acquired within the last six months.

Results

Of 3,190 evaluation specimens, 39 were confirmed as HIV-positive (12 with early infection) and 3,133 were HIV-negative by reference testing. DHC sensitivity was 87.2% overall and 94.4% and 0% for the antibody and antigen components, respectively. Sensitivity in early infection was 66.7% (all DHC antibody reactive) and the DHC antigen component detected none of nine HIV p24 antigen positive specimens. Median HIV RNA was higher in false negative than true positive cases (238,025 vs. 37,591 copies/ml; p = 0.022). Specificity overall was 99.4% with the antigen component contributing to 33% of false positives.

Conclusions

The DHC antibody component detected two thirds of those with early infection, while the DHC antigen component did not enhance performance during point of care HIV testing in a high risk clinic-based population.