Evaluation of ‘Q-PREVEN’ an HIV-1/2 Assay Developed Specifically for the Detection of Antibodies on Dried Blood Spots
Introduction: Simple sampling methods that can be applied under difficult field conditions are needed to expand access to diagnosis and treatment. Q-Preven HIV 1+2 (Symbiosis Diangnóstica, Brazil), is an enzimeimmunoassay (ELISA) developed for the detection of antibodies against all strains of HIV specifically in whole blood collected and dried on filter paper (DBS). Our objective was to determine the sensitivity, specificity and predictive values of Q-Preven. We also evaluated the stability of HIV antibody detection on DBS stored at ambient temperature for a period of 35 days.
Methods: 309 sera and DBS samples were collected in parallel from blood donors and patients attending a reference hospital in southern Brazil from December to January, 2005. Samples were tested according to the manufacturer´s instruction. DBS was screened for the presence of antibodies to HIV by Q-Preven, and sera by ELISA (Cobas Core, Abbott Axsym HIV-1/2 gO) and HIV RNA reference tests (Bayer bDNA, v3.0). The performance characteristics of Q-Preven were calculated using the reference protocol as the gold standard. Samples with discordant results from the reference were retested in triplicate.
Results: Two hundred and one samples were HIV negative (65%), and 108 were HIV positive (35%) resulting in the following performance data in the first run: sensitivity 100% (95%CI 97.9-100%); specificity 99.5% (95%CI 98.4-99.5%); PPV 99,1%( 95%CI 97%-99%%); NPV 100% (95%CI 98,9-100%). It is noteworthy that the initial discordant sample (false-positive) was retested resulting in triplicate concordant results. Analyses of stability with high titer positive samples demonstrated no decrease over time in the mean OD ratios after 35 days of room temperature storage.
Conclusions: Q-Preven demonstrated high performance characteristics. The requirement of less blood volume, easy storage and transportation make the assay ideal for use in areas where specimens have to be sent to a centralized testing facility, especially in resource limited settings.
De Souza R.1, Borges L.G.1, Motta L.1, Cauduro de Castro A.2
1Laboratório de Pesquisa em HIV/AIDS, Universidade de Caxias do Sul, Caxias do Sul, Brazil, 2Hospital Nossa Senhora da Conceição, Porto Alegre, Brazil