title: Attrition in longitudinal randomized controlled trials: home visits make a difference.
abstract: BACKGROUND
  Participant attrition in longitudinal studies can introduce systematic bias, favoring participants who return for follow-up, and increase the likelihood that those with complications will be underestimated. Our aim was to examine the effectiveness of home follow-up (Home F/U) to complete the final study evaluation on potentially "lost" participants by: 1) evaluating the impact of including and excluding potentially "lost" participants (e.g., those who required Home F/U to complete the final evaluation) on the rates of study complications; 2) examining the relationship between timing and number of complications on the requirement for subsequent Home F/U; and 3) determining predictors of those who required Home F/U.
  
  
  METHODS
  We used data from a randomized controlled trial (RCT) conducted from 1991-1994 among coronary artery bypass graft surgery patients that investigated the effect of High mean arterial pressure (MAP) (intervention) vs. Low MAP (control) during cardiopulmonary bypass on 5 complications: cardiac morbidity/mortality, neurologic morbidity/mortality, all-cause mortality, neurocognitive dysfunction and functional decline. We enhanced completion of the final 6-month evaluation using Home F/U.
  
  
  RESULTS
  Among 248 participants, 61 (25%) required Home F/U and the remaining 187 (75%) received Routine F/U. By employing Home F/U, we detected 11 additional complications at 6 months: 1 major neurologic complication, 6 cases of neurocognitive dysfunction and 4 cases of functional decline. Follow-up of 61 additional Home F/U participants enabled us to reach statistical significance on our main trial outcome. Specifically, the High MAP group had a significantly lower rate of the Combined Trial Outcome compared to the Low MAP group, 16.1% vs. 27.4% (p=0.032). In multivariate analysis, participants who were ≥ 75 years (OR=3.23, 95% CI 1.52-6.88, p=0.002) or on baseline diuretic therapy (OR=2.44, 95% CI 1.14-5.21, p=0.02) were more likely to require Home F/U. In addition, those in the Home F/U group were more likely to have sustained 2 or more complications (p=0.05).
  
  
  CONCLUSIONS
  Home visits are an effective approach to reduce attrition and improve accuracy of study outcome reporting. Trial results may be influenced by this method of reducing attrition. Older participants, those with greater medical burden and those who sustain multiple complications are at higher risk for attrition.
authors.affiliation: Division of Clinical Epidemiology and Evaluative Sciences Research, Weill Cornell Medical College, 1300 York Avenue, Box 46, New York, NY 10065, USA. jcpeters@med.cornell.edu
authors.forename: Janey C
authors.initials: JC
authors.lastname: Peterson
authors.forename: Paul A
authors.initials: PA
authors.lastname: Pirraglia
authors.forename: Martin T
authors.initials: MT
authors.lastname: Wells
authors.forename: Mary E
authors.initials: ME
authors.lastname: Charlson
mesh_terms: D000368:Aged; D062186:Arterial Pressure; D001026:Coronary Artery Bypass / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006792:House Calls / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D010358:Patient Participation / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic