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.
The Kirby Institute, University of New South Wales, Sydney, New South Wales, Australia.
Damian P
DP
Conway
Centre for Social Research in Health, University of New South Wales, Sydney, New South Wales, Australia.
Martin
M
Holt
Sydney Sexual Health Centre, Sydney Hospital, Sydney, New South Wales, Australia; School of Public Health and Community Medicine, University of New South Wales, Sydney, New South Wales, Australia.
Anna
A
McNulty
Western Sydney Sexual Health Centre, Western Sydney Local Health District, Sydney, New South Wales, Australia; Sydney Emerging Infections and Biosecurity Institute, University of Sydney, Sydney, New South Wales, Australia.
Deborah L
DL
Couldwell
School of Public Health and Community Medicine, University of New South Wales, Sydney, New South Wales, Australia; Albion Centre, Surry Hills, Sydney, New South Wales, Australia.
Don E
DE
Smith
North Shore Sexual Health Service, Royal North Shore Hospital, St Leonards, Sydney, New South Wales, Australia.
Stephen C
SC
Davies
St Vincent's Centre for Applied Medical Research, University of New South Wales, Sydney, New South Wales, Australia; NSW State Reference Laboratory for HIV, St Vincent's Hospital, Darlinghurst, Sydney, New South Wales, Australia.
Philip
P
Cunningham
The Kirby Institute, University of New South Wales, Sydney, New South Wales, Australia.
Phillip
P
Keen
The Kirby Institute, University of New South Wales, Sydney, New South Wales, Australia.
Rebecca
R
Guy
D000328:Adult; D000554:Ambulatory Care Facilities; D015483:HIV Antibodies / Q000276:immunology*; D015658:HIV Infections / Q000175:diagnosis* / Q000276:immunology; D006679:HIV Seropositivity / Q000175:diagnosis* / Q000276:immunology; D006801:Humans; D008297:Male; D008403:Mass Screening; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012680:Sensitivity and Specificity
D015483:HIV Antibodies; D011933:Reagent Kits, Diagnostic