Evaluation of the Bio-Rad Multispot HIV-1/HIV-2 Rapid Test as an alternative to Western blot for confirmation of HIV infection.

Background: In the United States, a new HIV diagnostic algorithm has been proposed that uses an HIV-1/HIV-2 antibody differentiation immunoassay instead of Western blot or immunofluoresence for confirmatory testing.

Objectives: To evaluate the Multispot HIV-1/HIV-2 Rapid Test (Multispot) as an alternative to Western blot analysis for confirmation of HIV infection.

Study Design: A series of 205 serum and plasma specimens positive for HIV-1 or HIV-2 were used to compare the performance of Multispot to a standard HIV-1 Western blot. Positive samples included 63 specimens from patients>18 months of age, 33 proficiency survey specimens, and 109 specimens from nine commercial seroconversion and performance panels. In addition, 63 specimens from 51 HIV-exposed, uninfected children≤18 months of age in various stages of seroreversion and 192 HIV-negative samples were tested. Specimens were initially screened using a 4th generation HIV Ag/Ab Combo assay.

Results: Multispot readily discriminated between individuals with HIV-1 or HIV-2 infection and those who were uninfected. Of the 205 samples repeatedly reactive by the 4th generation screening assay, infection status was correctly confirmed by Multispot in 83.9% (172/205) compared to 68.8% (141/205) for Western blot. Multispot detected HIV-1 earlier in 27.6% of low-titer antibody specimens called indeterminate by Western blot, and effectively reduced the number of indeterminate results in seroreverting HIV-1 exposed, uninfected infants and for HIV-2 infections misinterpreted as indeterminate or positive by HIV-1 Western blot.

Conclusions: Multispot offers speed and simplicity over Western blot and has an excellent performance for differentiation and confirmation of antibodies to HIV-1 and HIV-2.