Virological exploration of individuals with discordant HIV screening tests

Clinical application evaluation of two fourth-generation human immunodeficiency virus (HIV) screening assays in West China Hospital

BACKGROUND

Fourth-generation human immunodeficiency virus (HIV) screening assays have been used in many laboratories. The Elecsys® HIV combi PT assay is a new kind of fourth-generation HIV screening assay developed to allow earlier detection of seroconversion.

METHODS

A total of 271,845 routine specimens were detected using the Elecsys® HIV combi assay and Elecsys® HIV combi PT assay from September 2010 to December 2012 in a large university hospital. Repeatedly, reactive screening samples were confirmed according to recommended confirmatory algorithms.

RESULTS

The false-positive rate and positive predictive value (PPV) of two assays are 0.08 and 78.35%, respectively, for the Elecsys® HIV combi assay and 0.07 and 82.21% for the Elecsys® HIV combi PT assay. Ninety-four percent cases with cutoff index ratio <15.0 were false-positive. When we set the specificity as 95.0 and 99.0%, PPV could increase to 98.7, 99.6, 98.8, and 99.7%, and sensitivity reduced to 99.2, 98.4, 98.5, and 96.8% for the Elecsys® HIV combi assay and the Elecsys® HIV combi PT assay, respectively.

CONCLUSIONS

The Elecsys® HIV combi PT assay shows a better performance in specificity than the Elecsys® HIV combi assay. Most weakly reactive results were false-positive, this means it still need to be improved and it will need laboratory personnel to communicate with the clinical doctor and patients more properly about the result of the assay.

Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States

Serodiagnosis of human immunodeficiency virus (HIV) infection in the United States has traditionally relied on a sequential two-test algorithm: an initial screen with an enzyme immunoassay (EIA) and reflex testing of EIA-reactive specimens with a more specific supplemental test such as Western blotting or immunofluorescence. The supplemental tests are tedious, subjective, and expensive. In addition, there have been major improvements in the performance and accuracy of the EIA tests as well as the introduction of rapid serologic tests (RT) and HIV nucleic acid amplification tests (NAAT). Related to these improvements is the possibility that alternative algorithms using combinations of currently approved HIV tests may function as well as if not better than the current algorithm, with more flexibility, improved accuracy, and lower cost. To this end, we evaluated the performance of 12 currently licensed tests and 1 in-house HIV test (6 EIA, 4 RT, and 3 NAAT) on panels of plasma samples from HIV-infected (n = 621 HIV type 1 [HIV-1] and 34 HIV-2) and uninfected (n = 513) people and of sequential specimens from people early in seroconversion (183 specimens from 15 patients). Test combinations were analyzed in two dual-test (sensitivity-optimized and specificity-optimized) algorithms and in a three-test (tie-breaking) algorithm, and performance was compared to the conventional algorithm. The results indicate that alternative algorithm strategies with currently licensed tests compare favorably with the conventional algorithm in detecting and confirming established HIV infection. Furthermore, there was a lower frequency of discordant or indeterminate results that require follow-up testing, and there was improved detection of early infection.

Communicating indeterminate HIV Western blot test results to clients: an observational study of three community testing sites

This study examined HIV test counselors' beliefs and practices regarding communicating indeterminate HIV test results to clients. There are many reasons for an indeterminate HIV antibody/ Western blot assay including early HIV infection, infection with other contagious diseases, autoimmune diseases, and second or subsequent pregnancies in women. Field observations of three community HIV testing sites and semistructured interviews with 16 HIV test counselors were conducted from August 2002 through June 2003. Counselors defined an indeterminate test result in different ways. They also presented several different theories of causation, yet failed to mention two potential causes of an indeterminate result, association with large animals and infection with other (non-HIV-1) HIV strains. Counselors' understanding of the meaning of an indeterminate HIV test result varied a great deal. Some counselors believed that an indeterminate result truly was ambiguous while others believed it was indicative of being either HIV-positive or HIV-negative. Counselors' primary advice to clients who received an indeterminate result was to retest immediately without a waiting period. Counselors reported that communicating indeterminate test results to clients was a challenging task because clients who received such a result were confused, angry, and/or mistrustful. Results highlight the need for further research to provide reliable estimates of the extensiveness of indeterminate HIV test results and to further assess the nature of counselor and client responses to indeterminate test results.