title: Loss of follow-up in orthopaedic trauma: is 80% follow-up still acceptable?
abstract: BACKGROUND
  Loss of follow-up represents a potential source of bias. Suggested guidelines propose 20% loss of follow-up as acceptable. However, these guidelines have not been established through scientific investigations. The goal of this study was to evaluate how loss of follow-up influences the statistical significance in a trauma database.
  
  
  METHODS
  A database of 637 polytrauma patients with an average follow-up of 17.5 years postinjury was used. The functional outcome of workers' compensation patients versus nonworkers' compensation patients was compared using a validated scoring system. A significant difference between the 2 groups was found (P < 0.05). We simulated a gradually increasing loss of follow-up by randomly deleting an increasing number of patients from 2%, 5%, and 10%, and then increasing in increments of 5% until the significance changed. This process was repeated 50 times, each time with a different electronic random generator. For each simulation series, we documented at which simulated loss of follow-up that the results turned from significant (P < 0.05) to nonsignificant (P > 0.05).
  
  
  RESULTS
  Among 50 simulation series, the turning point from significant to nonsignificant varied between 15% and 75% loss of follow-up. A simulated loss of follow-up of 10% did not change the statistical significance in any of the simulation series; a simulated loss of follow-up of 20% changed the statistical significance in 28% of our simulation series.
  
  
  CONCLUSIONS
  A loss of follow-up of 20% or less may frequently change the study results. Researchers should establish protocols to minimize loss of follow-up and clearly state the loss of follow-up in manuscript publications.
authors: Division of Orthopaedic Traumatology, Department of Orthopaedic Surgery, UT Health Science Center at San Antonio, San Antonio, TX 78229, USA. boris.zelle@gmail.com
authors: Boris A
authors: BA
authors: Zelle
authors: Mohit
authors: M
authors: Bhandari
authors: Alvaro I
authors: AI
authors: Sanchez
authors: Christian
authors: C
authors: Probst
authors: Hans-Christoph
authors: HC
authors: Pape
mesh_terms: D015982:Bias; D006801:Humans; D059012:Lost to Follow-Up; D008962:Models, Theoretical; D009141:Musculoskeletal System / Q000293:injuries*; D016896:Treatment Outcome; D014942:Workers' Compensation; D014947:Wounds and Injuries / Q000453:epidemiology*