Theophylline for Irreversible Chronic Airflow Limitation: AnalysisA sample of 80 patients was chosen based on a two-tailed a-error of 5%, 80% power, a 20% loss to follow-up, and the use of the CRQ Physical and Emotional function scores and the 6-min walk as primary outcomes. Minimal important differences for within-group changes over 1 year were assumed to be 4.5 for the Physical Function score, 5.5 for the Emotional Function score, and 30 m for the 6-min walk. Estimates for within-group variance over time for these measures were derived from our previous trial. An a priori sample size estimate for the differences in drug usage between the two groups was not done because it was a secondary hypothesis.
Analysis
Two-way analyses of variance, accounting for the randomization strata and n of 1 trial or standard practice therapy, were performed. The effects of interest were the changes from baseline at 6 and 12 months in the CRQ Physical and Emotional Function scores and in the 6-min walk. The primary analysis compared all n of 1 trial patients to all standard practice patients. A prespecified secondary analysis compared n of 1 trial patients to standard practice patients within the prior-theophylline-use and no-prior-theophylline-use strata. The level of statistical significance was set at 5% (two-tailed) and was not adjusted for multiple comparisons. Allergy relief other Similar analyses were performed for changes in FEV1 and FVC. Comparison of proportions between groups used the normal approximation to the binomial distribution, provided that the expected values within each cell of the contingency table exceeded 5. If at least one of the expected values was < 5, proportions were compared by Fisher’s exact test. Ninety-five percent CLs for differences between groups were based on the normal approximation to the binomial distribution for proportions and Student’s t distribution for means. Measures of patient and physician confidence in the treatment decision were assessed by the Mann-Whitney U test. All results shown have used an intent-to-treat rule and include all available data on patients withdrawn from the study to the time of withdrawal, unless otherwise indicated.