title: Dropout rates for intent-to-treat and per protocol analyses.
abstract: OBJECTIVE
  To describe dropout rates for the intent-to-treat and per protocol analyses from prospective clinical trials.
  
  
  METHODS
  Review of prospective multi-center parallel studies of 100 patients or more from 1996 onwards.
  
  
  RESULTS
  We identified 33 articles (70 treatment arms) that fit the criteria for this study. No statistical differences in dropout rates were observed among drug classes for either the intent-to-treat (P =.075) or per protocol analyses (P =.40). A difference was observed in the percent dropout rate for the intent-to-treat analyses decreasing with the length of the study (P <.0001). This finding was not observed by the number of study visits (P =.44). However, a statistically greater percent dropout rate was observed for the per protocol analyses increasing with the length of the study (P =.034) and number of study visits (P =.01). No statistical differences were observed or with increasing sample size of the study for either the intent-to-treat or per protocol analyses (P >.05).
  
  
  CONCLUSIONS
  Known discontinuation rates for per protocol and intent-to-treat analyses may help in planning sample sizes for future clinical trials.
authors.affiliation: Pharaceutical Research Network, and Carolina Eye Institute, University of South Carolina School of Medicine, Columbia, South Carolina 29412-2464, USA. prnc@bellsouth.net
authors.forename: William C
authors.initials: WC
authors.lastname: Stewart
authors.forename: Angi L
authors.initials: AL
authors.lastname: Jackson
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Jenkins
mesh_terms: D000959:Antihypertensive Agents / Q000627:therapeutic use*; D002985:Clinical Protocols; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data*; D005901:Glaucoma / Q000188:drug therapy*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D015233:Models, Statistical; D009798:Ocular Hypertension / Q000188:drug therapy; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012107:Research Design; D012494:Sampling Studies
chemical_list: D000959:Antihypertensive Agents