Authors: Eligius F Lyamuya (corresponding author) [1]; Said Aboud [1]; Willy K Urassa [1]; Jaffer Sufi [1]; Judica Mbwana [1]; Faustin Ndugulile [2]; Charles Massambu [2]
Background
Several types of assays for HIV antibody detection have been developed and promoted for HIV screening and diagnosis. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used technique for screening purposes followed by confirmatory testing, most commonly by using Western blot (WB) assay or a second ELISA based on a different test principle and antigen source in an alternative confirmatory strategy. Simple rapid HIV assays which do not require use of instruments have been widely used especially in resource limited settings including African countries. Currently there are many different commercially available ELISAs, as well as simple rapid HIV assays for detection of antibodies to HIV. Evaluation of various anti-HIV-1 assays using panels of American and European sera have shown that most of these assays have a high sensitivity and specificity [1]. However, studies have shown that some of these assays do not have a similar test performance when used for testing of African sera [2]. It is therefore generally recommended to evaluate HIV assays in the context in which they will be used before adopting them for wide scale use [3, 4].
Various combinations of ELISAs as alternative confirmatory strategies have been shown to have the same diagnostic accuracy as the use of antibody ELISA followed by WB assay [5]. In recent years, interest has centred on the use of simple rapid HIV assays, especially in voluntary counselling and testing (VCT) facilities. Suitable algorithms based on a combination of two or more simple rapid assays have been shown to have diagnostic accuracy comparable to double ELISA or double ELISA and WB testing strategies [6, 7, 8, 9]. Current initiatives and interventions for prevention of mother-to-child transmission (PMTCT) of HIV-1 require the use of simple rapid assays in VCT services and antenatal clinics aiming at giving same day results. The World Health Organization (WHO) performance characterization of rapid HIV tests shows that a number of assays perform very well using international panels of blood samples. Likewise, new assays entering the diagnostics market address both performance characteristics and operational requirements that allow expansion of access to HIV testing in resource-constrained countries.
The current rapid HIV testing algorithm which is in use in Tanzania was developed 6 years ago [10]. This serial testing algorithm is based on the use of Capillus HIV-1/2 assay (Trinity Biotech, Ireland) for screening followed by confirmatory testing of reactive samples by Determine[TM] HIV-1/2 assay (Abbott Diagnostics, UK) [10]. Capillus assay requires cold storage, making it unsuitable for use in hard to reach areas where electricity is not available or in settings where power outages are frequent. The cold chain dependency for Capillus assay coupled with availability on the market, of newer HIV rapid tests that are cheaper, do not require cold storage and have acceptable performance characteristics compelled the Ministry of Health and Social Welfare to embark on evaluation of some of these rapid HIV assays aiming at developing alternative algorithms for use in Tanzania. Furthermore, there is an urgent need within the country for a suitable algorithm(s) that meet the demand for the scale up of access to HIV screening, diagnosis, treatment and care in line with the Ministry of Health and Social Welfare Strategic Plan for Prevention, Treatment and Care for HIV/AIDS.
The aims of this study were to evaluate the performance of five simple rapid HIV assays using whole blood samples from hospital patients, pregnant women, VCT attendees and blood donors, and to formulate an alternative cost-beneficial confirmatory strategy based on rapid HIV testing algorithms suitable for use in Tanzania.
Methods
Selection of Rapid HIV Assays for Evaluation
The rapid HIV assays …
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