Clinical trial participants compared with nonparticipants in cystic fibrosis

Am J Respir Crit Care Med. 2006 Jan 1;173(1):98-104. doi: 10.1164/rccm.200502-273OC. Epub 2005 Sep 28.


Rationale: The randomized clinical trial has been an important tool for expanding our knowledge of disease. This study is the first to compare trial participants to the entire eligible population.

Methods: We performed a cohort analysis using data from the Cystic Fibrosis Foundation Registry database between 1992 and 1998.

Measurements and main results: There were 8,735 patients older than 6 yr followed for the entire period. Of the patients, 2,635 patients (30.2%) were enrolled in at least 1 of 32 Institutional Review Board-approved clinical trials, with an average annual participation rate of 7%. Patients enrolled in clinical trials had more advanced disease as judged by FEV(1)% predicted (68 vs. 77%, p < 0.001), higher rates of Pseudomonas aeruginosa infection (71 vs. 65%, p < 0.01), and were more likely to have private insurance (odds ratio [OR], 1.25; 95% confidence interval [CI], 1.14-1.37) and be white (OR, 1.98; 95% CI, 1.44-2.70). No sex differences were noted. Despite the worse clinical status at baseline, clinical trial participants had a lower average annual rate of decline in lung function (1.33%/yr; 95% CI, 1.20, 1.46; compared with 1.52%; 95% CI, 1.43-1.60).

Conclusions: These results show that the overall participation rate is very high. Despite more advanced disease at baseline, lung function decline was lower in trial participants; the cause of this difference is unclear. The differences seen in insurance status are concerning. Efforts should be made to ensure adequate representation from different social demographic groups.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Cohort Studies
  • Cystic Fibrosis*
  • Delivery of Health Care*
  • Female
  • Humans
  • Male
  • Patient Acceptance of Health Care
  • Patient Selection
  • Randomized Controlled Trials as Topic*