Assessment of WHO strategy for HIV testing using results of the Royal Thai Army (RTA) serosurveillance data

2.0%. The false positive rate of the two sequential 3 rd -generation ELISAs was 0.58% (644/111,639). The PPV of Abbott testing alone was 77.3% (2,195 of 2,839), whereas the PPV of two sequential ELISAs was 94.5% (2,195 of 2,322). This study confirmed that sequential use of two 3 rd generation ELISAs increased the PPV of HIV testing. Six per thousand HIV false positive results might occur in a low prevalence population that used two sequential 3 rd -generation ELISA tests alone. Such a false positivity rate (<1%) makes sequential use of 2 ELISAs a very good tool for surveillance in saving cost, but not for clinical diagnosis due to a finite number of misdiagnosed individuals.