title: Systematic bias in outcome studies of persons with traumatic brain injury.
abstract: OBJECTIVE
  (1) Examine systematic biases created by subjects lost at 1-year follow-up in samples of persons with traumatic brain injury; (2) identify potential threats to generalization of outcomes data.
  
  
  METHODS
  A consecutive sample of admissions to acute rehabilitation studied 1 year following discharge.
  
  
  METHODS
  An inpatient brain injury rehabilitation unit in a large, academic medical center.
  
  
  METHODS
  Eighty-eight patients with primary diagnosis of traumatic brain injury.
  
  
  METHODS
  Subjects were considered lost to follow-up when phone calls, mail, clinic visits, and assistance from family failed to allow contact 1 year after discharge from acute rehabilitation. Potential effects of the biased follow-up sample were examined for seven suboptimal outcomes.
  
  
  RESULTS
  A total of 38.6% of subjects were lost to follow-up. Subjects intoxicated at time of injury and those with history of substance abuse were more-likely to be lost. Among subjects followed, the likelihood of working or being in school 1 year after discharge was significantly less for those intoxicated at time of injury and those with a history of substance abuse.
  
  
  CONCLUSIONS
  Systematic bias in longitudinal studies may result from subjects with substance use problems being lost to follow-up. Population estimates for return to work or school will be overestimated if those lost who have substance use problems resemble those followed.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Ohio State University, Columous, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Corrigan
authors.forename: J A
authors.initials: JA
authors.lastname: Bogner
authors.forename: W J
authors.initials: WJ
authors.lastname: Mysiw
authors.forename: D
authors.initials: D
authors.lastname: Clinchot
authors.forename: L
authors.initials: L
authors.lastname: Fugate
mesh_terms: D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000209:etiology / Q000534:rehabilitation*; D000431:Ethanol / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D017063:Outcome Assessment, Health Care; D019966:Substance-Related Disorders / Q000150:complications
chemical_list: D000431:Ethanol