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Background The Determine™ HIV-1/2 Ag/Ab Combo (DC) rapid test can identify HIV-1 infection earlier than rapid antibody-only tests in plasma specimens. Objectives We compared the performance of DC with a laboratory-based antigen/antibody (Ag/Ab) combo assay in plasma and evaluated antigen reactivity in whole blood specimens. Study design We tested by DC 508 plasma specimens collected in a prospective study and 107 sequential plasma and simulated whole blood specimens from 20 seroconversion panels. Previous results using the ARCHITECT (ARC) Ag/Ab combo assay were compared to DC results. In seroconversion panels, the days from the first HIV1 RNA-positive test to first DC-reactive in plasma and whole blood was compared. McNemar’s and Wilcoxon signed rank tests were used for statistical analysis. Results Of 415 HIV-positive samples, ARC detected 396 (95.4%) and DC 337 (81.2%) ( p < 0.0001 ). DC was reactive in 50.0% of ARC-reactive/MS-negative, 78.6% of ARC-reactive/MS-indeterminate, and 99.6% of ARC-reactive/MS-HIV-1-positive or −undifferentiated specimens. DC antigen reactivity was higher among ARC-reactive/MS-negative than MS-indeterminate samples. In 20 HIV-1 seroconversion panels, there was a significant difference between DC reactivity in plasma (91.1%) and whole blood (56.4%) ( p < 0.0001 ). DC with whole blood showed a significant delay in reactivity compared to plasma ( p = 0.008 ). Conclusions In plasma, DC was significantly less sensitive than an instrumented laboratory-based Ag/Ab combo assay. DC in plasma was significantly more sensitive compared to whole blood in early HIV-1 infections. With the U.S. laboratory-based diagnostic algorithm, DC as the first step would likely miss a high proportion of HIV-1 infections in early stages of seroconversion. [ABSTRACT FROM AUTHOR]

Objective FDA-approved antigen/antibody combo and HIV-1/2 differentiation supplemental tests do not have claims for dried blood spot (DBS) use. We compared two DBS-modified protocols, the Bio-Rad GS HIV Combo Ag/Ab (BRC) EIA and Geenius™ HIV-1/2 (Geenius) Supplemental Assay, to plasma protocols and evaluated them in the CDC/APHL HIV diagnostic algorithm. Methods BRC-DBS p24 analytical sensitivity was calculated from serial dilutions of p24. DBS specimens included 11 HIV-1 seroconverters, 151 HIV-1-positive individuals, including 20 on antiretroviral therapy, 31 HIV-2-positive and one HIV-1/HIV-2-positive individuals. BRC-reactive specimens were tested with Geenius using the same DBS eluate. Matched plasma specimens were tested with BRC, an IgG/IgM immunoassay and Geenius. DBS and plasma results were compared using the McNemar's test. A DBS-algorithm applied to 348 DBS from high-risk individuals who participated in surveillance was compared to HIV status based on local testing algorithms. Results BRC-DBS detects p24 at a concentration 18 times higher than in plasma. In seroconverters, BRC-DBS detected more infections than the IgG/IgM immunoassay in plasma ( p = 0 . 0133), but fewer infections than BRC-plasma ( p = 0 . 0133) . In addition, the BRC/Geenius-plasma algorithm identified more HIV-1 infections than the BRC/Geenius-DBS algorithm ( p = 0 . 0455) . The DBS protocols correctly identified HIV status for established HIV-1 infections, including those on therapy, HIV-2 infections, and surveillance specimens. Conclusions The DBS protocols exhibited promising performance and allowed rapid supplemental testing. Although the DBS algorithm missed some early infections, it showed similar results when applied to specimens from a high-risk population. Implementation of a DBS algorithm would benefit testing programs without capacity for venipuncture. [ABSTRACT FROM AUTHOR]