Assays for HIV with improved sensitivity and specificity

Evaluation of Four Simple/Rapid Assays and Two Fourth-Generation ELISAs for the Identification of HIV Infection on a Serum Panel Representing the HIV-1 Group M Genetic Diversity in Cameroon

The performance of 4 rapid and simple assays: Camstix-HIV 1+2 (Camdiagnostix, Yaounde, Cameroon); Determine HIV 1+2+0 (Abbott Laboratories, Tokyo, Japan); Genie II HIV-1/HIV-2 (Bio-Rad, Marnes la Coquette, France); ImmunoComb II HIV 1 & 2 BiSpot (Orgenics, Yavne, Israel); and 2 fourth-generation ELISAs: Enzygnost HIV Integral (Dade Behring, Marburg, Germany) and Genscreen plus HIV Ag-Ab (Bio-Rad, Marnes la Coquette, France) currently used in Cameroon to detect HIV infections were evaluated on a local serum panel. A total of 503 samples were collected, using the Camstix-HIV 1+2 assay. Overall, 280 samples were confirmed HIV positive, 181 were negative, and 42 were indeterminate. All positive samples belonged to group M: CRF02_AG (73.5%), A1 (7.1%), A2 (1.2%), G (4.7%), F2 (5.1%), D (1.6%), CRF11 (1.6%), CRF06 (1.2%), and CRF01_AE (1.6%). Sensitivity, specificity, test efficiency, and positive and negative predictive values were calculated both including and excluding indeterminate samples. Except for Genie II and ImmunoComb II (98.9 and 99.3%, respectively), sensitivities were 100% for the remaining 4 tests. Specificities, efficiencies, and positive predictive values of all assays were negatively affected by the addition of HIV-indeterminate samples in the calculations. These data show the importance of prior test evaluations on local serum panels and in field conditions before a national policy for HIV screening is decided on and stress also the need to use tests and algorithms that can reduce the high number of HIV-indeterminate results in Africa.

Standardisation of subjectively scored HIV immunoassays: developing a quality assurance program to assist in reproducible interpretation of results using an anti-HIV particle agglutination assay as a model

Immunoassays such as particle agglutination assays, rapid tests and western or line blots are scored or read subjectively. These readings display intra- and inter-reader variability, as well as intra- and inter-laboratory variability. In the present study the consistency of scoring was assessed between readers both within and between two groups of scientists using the Serodia anti-HIV particle agglutination assay as an example of an assay scored subjectively. An anti-HIV positive sample in eight serial dilutions made to yield a full range of results expected for the assay was presented 12 times (96 test wells). Each dilution was placed randomly in a plate and tested with the Serodia anti-HIV particle agglutination assay then photographed. Participants in the two groups each scored the photographed plate independently and twice, 2 h apart. Each well was assigned a status (the consensus result of the four most experienced Australian readers) and each participant's results were compared with this status. The average percentage of wells assessed as 'correct' for the Group A participants was 86% (range 56-98%) and for the Group B participants was 67% 'correct' (range 46-88%). In general, strongly positive and negative wells were scored 'correctly'. The highest variations between scores were seen in the borderline positive dilutions +/- region. A quality assessment program based on the method used to obtain these results will be instituted in order to improve the consistency of scoring assays read subjectively.