A replicable model for achieving over 90% follow-up rates in longitudinal studies of substance abusers

The goals of this paper were to: (a) discuss the interface between dominant behavioral patterns of substance users and the development of a follow-up management model, (b) describe the components of the model, (c) present data regarding its effectiveness, (d) estimate the number of contacts for various follow-up rates, (e) explore the generalizability of the model across sub samples, and (f) present client outcome data that underscore the potential negative impact of low follow-up rates. The model has been used to follow-up over 12,000 research participants yielding over a 95% follow-up rate across seven studies (with over 90% completed within +/-14 days of their anniversary date). Using data from two of these studies (n = 2010, n = 632), 22 contacts or less captured 70% of the participants while 33 or 38 contacts or less captured 90% in the first and second studies, respectively. When outcome variables were compared based on 70% versus 90% follow-up, the results varied by study and within study. An examination of the effect of attrition on validity in these two samples demonstrated that even the traditionally acceptable 30% level of attrition can result in significant bias and that the nature of the bias is unpredictable.