title: Persistence pays off: follow-up methods for difficult-to-track longitudinal samples.
abstract: OBJECTIVE
  Evolving privacy and confidentiality regulations make achieving high completion rates in longitudinal studies challenging. Periodically reviewing the methods researchers use to retain participants throughout the follow-up period is important. We review the effectiveness of methods to maximize completion rates in a 1-year longitudinal study of repeat driving-under-the-influence (DUI) offenders.
  
  
  METHODS
  During the course of 21 months, we attempted to follow-up with 704 participants of a licensed residential treatment facility for repeat DUI offenders. High rates of lifetime Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, substance-use disorders (97.6%) and nonsubstance- or nongambling-related psychiatric disorders (44.5%) among the sample made tracking participants difficult. To locate participants and complete follow-up interviews, we obtained baseline information, contacted collaterals, sent mailed reminders, searched Internet databases, and gave a monetary incentive for completing study interviews.
  
  
  RESULTS
  We located 608 participants with active telephone numbers (87.4%) and completed interviews with 488 (70.1% of the entire eligible sample and 80.3% of those with active telephone numbers), after an average (SD) of 8.6 (9.1) calls (median = 5.0). Increasing the number of calls continued to yield additional completions at 10, 20, and 30 calls; at approximately 40 telephone calls, the potential return for additional calls did not justify the added effort.
  
  
  CONCLUSIONS
  These results suggest that researchers need to (1) employ more than 10 telephone calls to adequately track difficult-to-follow substance-using populations, and (2) prepare for a subsample of participants who might require more extensive contact. These results highlight the importance of using empirical guidelines to plan estimates for the number of contacts needed to achieve an adequate follow-up completion rate.
authors.affiliation: Division on Addictions, Cambridge Health Alliance, Medford, Massachusetts 02155, USA. jkleschinsky@challiance.org
authors.forename: John H
authors.initials: JH
authors.lastname: Kleschinsky
authors.forename: Leslie B
authors.initials: LB
authors.lastname: Bosworth
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Nelson
authors.forename: Erinn K
authors.initials: EK
authors.lastname: Walsh
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Shaffer
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology; D000437:Alcoholism / Q000453:epidemiology; D001334:Automobile Driving; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007407:Interviews as Topic / Q000379:methods*; D008137:Longitudinal Studies; D008297:Male; D010349:Patient Compliance; D016320:Substance Abuse Treatment Centers / Q000639:trends