Locating study subjects: predictors and successful search strategies with inmates released from a U.S. county jail

Minimizing loss to follow-up in longitudinal studies is critical. The purpose of this study was to examine the ability to locate subjects recently released from jail, identify predictors of being able to find a subject, and describe effective search strategies for this unique population. The sample for this cohort study included study subjects who were sought for interview after release from jail. Inmates in the San Francisco City and County Jail were enrolled in a randomized trial of incentives to improve follow-up for tuberculosis therapy after release from jail. Sociodemographic, health-related, and extensive locating information was collected during baseline interviews in jail. The main outcome was successful location of the subject. Study personnel recorded data on the number and nature of attempts made to find subjects in order to describe successful search strategies. Of 254 persons sought for the postrelease interview, 188 (74.0%) were found. Primary English speakers were more likely than Spanish speakers to be found (relative risk: 3.2, 95% confidence interval: 1.5-6.7, p = 0.002). Nearly one quarter of subjects (24%) were found back in jail, and the remainder were found in the community. Phone calls and letters to the subjects, and personal contacts to family and friends were successful strategies for 53% of the subjects. Seeking persons in programs, such as shelters and drug and alcohol programs, was successful in finding 18% of English-speaking subjects. Outreach efforts in sections of the city where Latinos spent time, including popular restaurants and community gathering places, were successful in finding 13% of Spanish-speaking subjects. We conclude that study subjects released from jails can be successfully located using well-defined search protocols tailored to the ethnicity of the sample and including a variety of strategies. Employment of bilingual personnel is important when a large proportion of subjects is monolingual and non-English speaking.