An evaluation of a self-generated identification code.

We describe a self-generated coding form used in a study of HIV prevention practices of college students and provide information on the success rate of matching questionnaires over a 3-year period using the form. The data for this study were from a longitudinal study of HIV risk-reduction practices of college students. In order to match questionnaires over the 3-year study period while maintaining anonymity, participants were asked to complete a self-generated identification form at each data collection point. In the second year of the project, we were able to successfully match 74.3% of the questionnaires to those returned during the first year using 6 to 8 of the code elements on the form, and in the third year, we were able to match 73% of questionnaires to those returned in the second year. Participants for whom questionnaires matched were more likely than participants with unmatched questionnaires to be white students enrolled as underclassmen.