RETENTION OF ASTHMATIC-PATIENTS IN A LONGITUDINAL CLINICAL-TRIAL

Background: Prevention of study patient attrition and assessment of it s impact on outcome data are problems that receive little attention de spite their obvious importance in asthma research. Objective: The medi cal, demographic, and psychologic characteristics of asthmatic childre n and adults who dropped out of a yearlong medication trial were asses sed to determine whether this group differed from those who completed the study, potentially introducing bias into the data set and interfer ing with completion of the study's objectives. Methods: Profiles of 36 2 adult and pediatric asthmatic patient dropouts from the multicenter trial were contrasted with profiles of those who completed the study. Despite a 1-month prerandomization screening, 24% of patients failed t o complete the trial for varied reasons, which largely included noncom pliance and treatment dissatisfaction. Results: Although attrition rat es were equal among adults and children, dropout-completer differentia tion was not. Adult completers did not differ from dropouts in any var iables. However, pediatric dropouts were more likely than completers t o be female (67% and 36%, p = 0.008) and to have more reactive airways (PD20, 2.29 +/- 1.32 and 5.2 +/- 1.23, p = 0.05), to have reduce scor es on tests of intelligence (Full Scale IQ, 102.2 +/- 2.6 and 112.5 +/ - 1.6, p = 0.002) and problem solving (Wisconsin Card Sorting Test Err or Scores, 39.8 +/- 4.1 and 29.1 +/- 2.0, p = 0.01), and to have incre ased behavioral problems (Child Behavior Checklist Total Problem Score , 60.7 +/- 2.5 and 53.6 +/- 1.1, p = 0.003). Conclusion: These finding s demonstrate the potential of patient attrition to bias outcome in cl inical trials and underscore the necessity of: (1) preventing its occu rrence, (2) correctly assessing its causes, and (3) determining its ul timate impact on study results. Strategies for each of these three tas ks should be implemented at the study's initial planning stages.