Field application studies of rapid HIV tests (RHTs) have provided valuable insight into acceptability and performance or RHTs, particularly specificity. However, field studies are unable to assess test sensitivity and limit of detection of different RHTs. Laboratory evaluation by testing larger numbers of specimens with acute and confirmed HIV infection is required.
We evaluated six candidate RHTs and conventional diagnostic laboratory assays on panels of well characterised serum and plasma samples. Samples from 50 antiretroviral treatment naïve individuals were tested with a HIV incidence ELISA and categorised as recent infection (within 155 days) (n=25) or established HIV infection (>155 days) (n=25). A further 59 samples from individuals with laboratory evidence of acute HIV infection (reactive fourth generation conventional HIV-1/2 Ag/Ab test, detectable HIV-1 p24 antigen or nucleic acid, negative or evolving HIV western blot) were used to assess test sensitivity in terms of limit of detection. Of the 59 acutely infected individuals, 38 had follow-up samples available (mean 6.89 days, range 2-7 days) from the index sample. A further 50 samples collected from individuals found to be seronegative by the conventional HIV-1/2 Ab/Ag 4th generation laboratory screening test were included to assess specificity.
Compared with the conventional laboratory test algorithm including Abbott Architect HIV 1/2 Ag/Ab combo , the sensitivity of the six rapid tests in acute infection was: Alere HIV-1/2 Ag/Ab Combo 87.5%; Alere HIV-1/2 Antibody 84.1%; Trinity Uni-Gold HIV-1/2 Antibody 76.3%; Insti HIV-1/2 Antibody 72.5%; Biorad Multispot HIV-1/2 Antibody 72.5%; and Orasure Oraquick HIV-1/2 Antibody 61.7%. Sensitivity in patients with known HIV infection for the rapid tests was 100%, except for the Orasure Oraquick HIV-1/2 Antibody (96.1%). Specificity for the rapid tests was 100%, except for the Orasure Oraquick HIV-1/2 Antibody (98.0%).
These results confirm that RHT’s are less sensitive than conventional laboratory tests in detection of acute HIV infection. The introduction of rapid tests at the point of care have been shown to be acceptable to men who have sex with men and provides an additional tool to potentially increase testing. However, our evaluation highlights systems are needed to ensure that men seeking RHTs who have a recent risk exposure, also have conventional HIV laboratory tests.
