Evaluation of SMARTube to Detect HIV Infection Before Seroconversion Using Standard Methods

The acute phase of HIV infection carries substantial risk of transmission; identification of acute-phase infections may offer opportunities to reduce that risk. SMARTube incubation of blood specimens is designed to stimulate in vivo-primed HIV-specific lymphocytes to produce HIV antibodies in vitro. The resulting supernatant (S-plasma) can be tested to identify acute infections with commercially available HIV assays. We assessed the performance of the SMARTube to identify acute HIV infections in studies at three developing country sites. We conducted HIV incidence studies in Ho Chi Minh City, Vietnam, and Bloemfontein and Rustenburg, South Africa. We estimated HIV incidence in cross-sectional samples and measured prospective incidence in uninfected women followed for up to 12 months. We incorporated SMARTube into the HIV testing algorithm at cross-sectional screening and monthly follow-up visits. We tested 1,384 persons in Vietnam, 1,145 women in Bloemfontein, and 538 persons in Rustenburg. Cross-sectional samples from 11 participants that tested positive with SMARTube after an initial unincubated negative test result (11 of 2,472; 0.4% of all specimens) were considered "potential acute" infections. Matching samples from 3 of the 11 (27.3%) were confirmed by polymerase chain reaction (PCR) testing. In follow-up of 355, 401, and 223 uninfected women in Vietnam, Bloemfontein, and Rustenburg, respectively, 11 seroconversions occurred in Bloemfontein and Rustenburg. In four of these incident infections (36.4%), SMARTube testing had resulted in earlier detection of HIV infection than the eventual seroconversion visits. In our field studies, pretreatment with SMARTube allowed the identification of acute HIV-1 infection in some new infections, but with a positive predictive value of 27%. Larger studies are needed to evaluate SMARTube as an alternative to technically challenging and costly enzyme immunoassay and PCR testing to detect acute HIV infection.