To the Editor.
—The article by Ms Gallo and colleagues1 on an oral mucosal transudate (OMT) system for human immunodeficiency virus type 1 (HIV-1) antibody testing cites sensitivity as an important characteristic of this type of test. The authors demonstrate that in the general population this test will perform well, with a negative predictive value of 99.9%. Little disease will escape undetected.However, the general population has a much lower prevalence of HIV than their study population, in which 673 of 3570 subjects were positive for disease. The positive predictive value of the enzyme immunoassay (EIA) component of this test decreases from 97.5% in their sample to only 40% when applied to the general population. The OMT Western blot performs better, since none of the 2897 HIV-negative subjects in the study had a positive Western blot test result. Some still had an indeterminate test result, though, so the positive
Ryder K. Usefulness of Oral Mucosal Transudate for HIV Antibody Testing. JAMA. 1997;277(20):1591. doi:10.1001/jama.1997.03540440025014