RESUMO
BACKGROUND: Alere™ HIV Combo is the only rapid and sensitive point-of-care 4th generation (antigen/antibody) HIV test newly available in Thailand which is advantageous of differentiating between positivity of antigen or antibody or both, especially in acute HIV infection (AHI). AHI in this study was defined by positive machine-based 4th generation test with measurable HIV-RNA but negative 3rd generation (IgM/IgG antibody only) tests. OBJECTIVE: To evaluate the performance characteristics of Alere™ HIV Combo. METHODS: Fifty stored plasma samples of subjects diagnosed with AHI were used to evaluate Alere™ HIV Combo. RESULTS: Of the 50 AHI samples, Alere™ HIV Combo was positive in 37 (74%): 5 with antibody positive only (R1), 26 with p24 antigen positive only (R2), and 6 with both p24 antigen and antibody positive (R3). Mean sample/cut-off (S/ CO) ratios from machine-based 4th generation test of R1, R2 and R3 were 21.55, 148.38 and 72.97 respectively as compared to 7.57 for the 13 non-reactive (NR) samples. The corresponding median log10 HIV-RNA of NR, R1, R2 and R3 were 5.59, 5.86, 7.00 and 6.61 copies/mL respectively. R2 and R3 had significantly higher S/CO and HIV-RNA than NR and R1. Alere™ HIV Combo detected mainly p24 antigen in AHI as seen in 32/50 (64%) subjects and could detect 11/50 (22%) antibody in AHI samples which were missed by the two 3rd generation HIV tests used in our testing algorithm. CONCLUSIONS: Alere™ HIV Combo is the ideal screening test in a setting with high AHI where machine-based 4th generation test is not available.
RESUMO
BACKGROUND: Same-day anti-HIV testing algorithm is recommended by Thai National Guidelines. We compared performance characteristics of algorithms used in a mobile clinic and a facility-based clinic for men who have sex with men (MSM) in Bangkok. METHODS: Mobile clinic samples collected from 4 saunas and 2 spa venues were tested by Alere DetermineTM HIV 1/2, followed by DoubleCheck GoldTM Ultra HIV 1/2 and SD Bioline HIV 1/2 3.0. All samples were re-tested at the Thai Red Cross Anonymous Clinic (TRCAC) by Architect HIV Ag/Ab or Elecsys HIV combi PT, followed by Alere DetermineTM HIV 1/2 and Serodia HIV 1/2. Non-reactive samples were tested by Aptima nucleic acid amplification test (NAAT) and reactive/inconclusive samples were tested by less-sensitive immunoassays (IA) and HIV-1 RNA to detect acute HIV infection (positive NAAT or non-reactive IA/positive HIV-1 RNA). RESULTS: Of 233 MSM, 36 (15.5%) had HIV infection diagnosed using mobile clinic algorithm. Two additional acute HIV cases (1 positive NAAT and 1 reactive Architect with detectable HIV-1 RNA) were diagnosed using TRCAC algorithm. The mobile clinic algorithm had a sensitivity of 94.9% (95% CI: 82.7, 99.4) and a specificity of 100% (95% CI: 98.1, 100). CONCLUSION: Use of whole blood on rapid test kits demonstrated satisfactory performance and allowed same-day HIV test result through a mobile clinic model. For populations with high HIV incidence, careful history taking to define the window period is crucial and repeat testing must be encouraged if the testing algorithm does not include 4th generation anti-HIV assay or NAAT.