Contamination with HIV antibody may be responsible for false positive results in specimens tested on automated platforms running HIV 4th generation assays in a region of high HIV prevalence
Fig 3
S/CO values of the positive test in S+/R- and S-/R+ discordant samples were generally close to the cut-off (weakly reactive).
(a) S-/R+ samples had S/CO values between 1.0 and 99.1. (The positive range of Roche assay is 1->1000); (b) S+/R- samples had S/CO values between 1.1 and 5.8 (the positive range of Siemens assay is 1->12).