HIV-1 western blot: development and assessment of testing to resolve indeterminate reactivity.

OBJECTIVE

To reduce the number of HIV-1 Western blot (WB)-indeterminates requiring follow-up and the time taken to provide a clear positive or negative result.

DESIGN

In the first of two stages, a testing and follow-up strategy was developed to resolve anti-HIV-1 status of WB-indeterminates. In the second stage, implementation of this strategy was assessed.

METHODS

After dividing indeterminates into four groups according to WB profile, samples were tested for anti-HIV-1, anti-HIV-2, anti-HTLV-I antibodies, and HIV-1 antigen using the most sensitive assays available. When testing failed to clarify anti-HIV-1 status, follow-up samples were taken to monitor changes in antibody status.

RESULTS

Samples in two out of the four indeterminate groups were negative for anti-HIV-1. The other two groups required additional testing and/or follow-up to distinguish reactivity caused by anti-HIV-1 from cross-reactivity.

CONCLUSION

Grouping HIV-1 WB-indeterminates according to profile allows a significant percentage to be reported as anti-HIV-1-negative, while additional testing may allow others to be reported as anti-HIV-1-positive. The remainder require a maximum of 3 months' follow-up to resolve anti-HIV-1 status.