Data on the Relationships of Signal-To-Cutoff Ratios of Elecsys HIV Antigen/Antibody and Elecsys Syphilis Assays to Subsequent Confirmatory Testing at an Academic Medical Center

A case of a false positive HIV antigen/antibody screen in a pregnant woman at delivery and the clinical importance of reviewing signal-to-cutoff ratio values

“…Chopra et al conducted a study which included approximately 30,000 patients. Echoing the Parkland Hospital study [1] , it related that 94 % of false positive samples had S/Co ratios below 10, and even recorded a true positive sample with a ratio nearing 4000 [6] . Similarly, a different study reported that in a low risk population, the PPV of an ARCHITECT test with a S/Co ratio below 15 was 0 % [12] .…”