Randomized controlled trials in cystic fibrosis (1966-1997) categorized by time, design, and intervention.

The improved prognosis of cystic fibrosis (CF) over the last three decades has been associated with an increased use of a range of treatments, but it is important that the use of an individual treatment is based on evidence. Well-designed randomized controlled trials (RCTs) are a robust method for evaluating the effectiveness of such treatments. We have developed a register of RCTs in CF and have studied when they were performed, their design, and what interventions were investigated. We identified 506 RCTs; 37.5% were identified solely as abstract reports in conference proceedings. There has been about a 30-fold increase in the number of RCTs in CF since 1966. A high proportion of the RCTs (72.7%) had a sample size of 30 or less, and only 8.7% were multicenter trials. Reporting of study design was poor: in 51.4% the report did not state whether there was any blinding in the trial design; 53.6% of studies were of crossover design. The most common interventions studied were antibiotic treatments and physiotherapy, but a number of commonly used therapies had been evaluated only in a small number of patients. Although the number of RCTs of interventions in CF patients has increased over the last 25 years, the sample sizes of these trials are generally too small to indicate whether the intervention was effective, and very few were multicenter. Future RCTs in CF are more likely to provide clinically useful answers if higher numbers of patients are recruited into large, well-designed multicenter trials. This should be a priority of the organization of future research in CF.