HIV VERTICAL TRANSMISSION RATE DETERMINATIONS ARE SUBJECT TO DIFFERING DEFINITIONS AND THEREFORE DIFFERENT RATES

The HIV infection status of a cohort of 600 prospectively followed chi ldren horn to HIV infected mothers was determined using HIV peripheral blood culture tests at 0, 3, and 6 months of age, HIV serology at gre ater than or equal to 15 months, and CDC AIDS criteria. We estimated t ransmission rates using five methods which differed in how HIV indeter minates are handled. These methods were applied at two points in time to illustrate effects of length of follow-up of the cohort on results. In January 1997, 30 months after the last birth, transmission rate es timates ranged from 15.5% (known positives/known positives x known neg atives) to 18.1% (known positives x those with one positive culture x deaths/entire cohort minus those lacking negative cultures at age grea ter than or equal to 5 months). Estimates ranged from 14.8% to 20.7% u sing the subcohort of 284 children followed greater than or equal to 1 2 months as of May 1993. These results indicate that methods for assig ning HIV infection status and for handling HIV indeterminates should b e carefully defined when estimating transmission rates. (C) 1998 Elsev ier Science Inc.