title: Longitudinal Assessment of Bariatric Surgery (LABS): retention strategy and results at 24 months.
abstract: BACKGROUND
  Retaining participants in observational longitudinal studies after bariatric surgery is difficult yet critical because the retention rate affects interpretation and generalizability of results. Strategies for keeping participants involved in such studies are not commonly published. The objective of this study was to review LABS retention strategies and present the 24-month retention data.
  
  
  METHODS
  The LABS Consortium monitors an observational cohort study of 2458 adults enrolled before bariatric surgery at 10 centers within the United States (LABS-2). To maximize data completeness, the investigators developed retention strategies, including flexible scheduling, a call protocol, reminder letters, abbreviated visit options, honoraria, travel reimbursement, providing research progress reports, laboratory results, newsletters, study website, and retention surveys. Strategies for locating participants included frequent updates of contact information, sending registered letters, and searching medical and public records.
  
  
  RESULTS
  At 12 and 24 months, 2426 and 2405 participants remained active, with vital status known for 98.7% and 97.3% and weight obtained for 95.2% and 92.2%, respectively. There were 148 missed visits (6.2%) at 24 months primarily because of inability to contact the participant. Only 15 (0.6%) active participants at 24 months missed all follow-up visits. Although 42 participants could not be located or contacted at 6 months, data were obtained for 23 (54.7%) of them at 12 months, and of the 52 participants who could not be located or contacted at 12 months, data were obtained for 18 (34.6%) at 24 months.
  
  
  CONCLUSIONS
  Longitudinal studies provide the ability to evaluate long-term effects of bariatric surgical procedures. The retention achieved in LABS is superior to that of many published reports but requires extensive effort and resources. This report identifies useful retention strategies. Further research is needed to identify the efficacy and cost-effectiveness of specific retention strategies.
authors.affiliation: University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA. gourashwf@upmc.edu
authors.forename: William F
authors.initials: WF
authors.lastname: Gourash
authors.forename: Faith
authors.initials: F
authors.lastname: Ebel
authors.forename: Kathy
authors.initials: K
authors.lastname: Lancaster
authors.forename: Abidemi
authors.initials: A
authors.lastname: Adeniji
authors.forename: Laurie
authors.initials: L
authors.lastname: Koozer Iacono
authors.forename: Jessie K
authors.initials: JK
authors.lastname: Eagleton
authors.forename: Anne
authors.initials: A
authors.lastname: MacDougall
authors.forename: Chelsea
authors.initials: C
authors.lastname: Cassady
authors.forename: Hallie
authors.initials: H
authors.lastname: Ericson
authors.forename: Walter
authors.initials: W
authors.lastname: Pories
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Wolfe
authors.forename: Steven H
authors.initials: SH
authors.lastname: Belle
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D050110:Bariatric Surgery / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D010349:Patient Compliance / Q000706:statistics & numerical data*; D010352:Patient Dropouts / Q000706:statistics & numerical data; D016896:Treatment Outcome; D055815:Young Adult
keywords: Attrition; Bariatric surgery; Follow-up; Longitudinal research; Retention