Immediately on stopping the n of 1 trial, the code was opened and the mean symptom score for each 10-day treatment period was determined. If the patient had received at least one treatment pair, the point estimate on the difference in mean symptom score within treatment pairs (theophylline minus placebo) was determined; if two or more treatment pairs were received, the 90% confidence limits (CLs) on this estimate were also deter-mined. If diary scores were not available for at least one treatment pair, a recommendation to stop or continue theophylline was made according to clinical judgment and patient preference. For all other n of 1 trials, the recommendation about theophylline therapy was guided by a previously described algorithm that considered the point estimate on the mean difference in symptom score and, where available, its 90% CLs (Fig 2). We accepted 90% CLs, rather than the conventional 95% CLs, in deciding about a treatment effect within the n of 1 trials as a compromise between the inherent low power of n of 1 trials having four or less treatment pairs and the need to avoid a type I (false-positive) statistical error. Assumptions implicit in the algorithm were that the minimal important difference for n of 1 trials using a 7-point Likert scale was a mean change of 0.5/symptom and that within-patient serial correlation in mean responses could be ignored.
Patients treated according to standard practice stopped taking theophylline review canadian healthcare mall. They were asked to contact the study physician if their dyspnea worsened. Theophylline was resumed if this deterioration was deemed, on clinical grounds, not to be secondary to a new problem (eg, a respiratory infection). If their dyspnea improved on resuming theophylline, they were asked to remain on the drug. Standard practice patients were reviewed 3 months after randomization, when their status concerning theophylline therapy was recorded.
Patients in both groups returned to their primary care physicians once the initial 3-month phase of the study was completed. Changes to their treatment including changes regarding theophylline were left to the discretion of the primary care physician.
Figure 2. Interpretation of n of 1 trial results.