Utility of quantitative enzyme immunoassay reactivity for predicting human immunodeficiency virus seropositivity in low- and high-prevalence populations

Laboratory testing for infection with the human immunodeficiency virus: established and novel approaches

The enzyme-linked immunosorbent assay (ELISA) and the Western blot are the primary tests for the diagnosis and confirmation of human immunodeficiency virus (HIV) infection. The ELISA, an inexpensive screening test for antibodies to HIV-1, is both sensitive and specific. The HIV-1 Western blot is a reliable confirmatory test following a repeatedly reactive ELISA. False-positive HIV-1 results with this sequence of tests are extremely rare but can occur, and test results that are inconsistent with clinical or other laboratory information should be questioned, repeated, or supplemented. The US Food and Drug Administration has also approved rapid and more accessible testing methods. Oral mucosal transudate and urine testing are noninvasive testing methods; rapid and home sample collection kits offer easier access to testing.

Evaluation of HIV serial and parallel serologic testing algorithms in Abidjan, Côte d'Ivoire

OBJECTIVE

To evaluate HIV serologic testing algorithms based on a combination of three enzyme linked immunosorbent assays (ELISA) for the confirmation of HIV infection in Abidjan, Côte d'Ivoire, where HIV-2 and HIV-1 non-B subtypes are prevalent.

METHODS

A total of 1069 human sera with known serologic status, in addition to a seroconversion and low titer antibody panel were initially tested by six ELISA to determine the sensitivity, specificity and delta values of the assays. On the basis of the performance of the assays, three ELISA (Enzygnost, ICE 1.0.2, and Vironostika) were selected for use in a parallel and serial testing algorithm in analyzing 8283 consecutively collected sera. In the parallel testing algorithm, sera concordantly reactive or non-reactive by Enzygnost and ICE 1.0.2 were considered as true positive or true negative, respectively. In the serial algorithm, sera reactive by Enzygnost were retested by ICE 1.0.2. Sera with discordant results were tested by Vironostika, and the results was considered definitive. All reactive sera, plus a random sample of negative sera were tested for confirmation by Peptilav. In addition, a random sample of reactive sera was tested by Western blot.

RESULTS

All ELISA had 100% sensitivity; specificities ranged from 96.8 to 100%. Positive and negative delta values of the ELISA were high (range, 6.89 to 46.07 and -2.05 to -5.75, respectively). Of the 8283 sera, 2054 were considered true positives and were correctly classified by the parallel testing algorithm (sensitivity, 100%). Of the 6229 true negative sera, 6226 were negative by the parallel testing algorithm (specificity, 99.95%). The sensitivity of the serial algorithm was 99.96%, and specificity was 99.95%. None of the 250 concordant ELISA-negative sera in the algorithm that were randomly tested in Peptilav was positive; similarly, all of the 103 concordant ELISA-positive sera were confirmed by Western blot. The three-ELISA algorithm resulted in reagent cost-savings of at least 50% compared with the Peptilav-based algorithm.

CONCLUSION

These results suggest that a combination of ELISA using different principles or antigens in a serial or parallel algorithm is an efficient and cost-effective alternative to the standard algorithm in areas where HIV-1 and HIV-2 are prevalent.