Theophylline for Irreversible Chronic Airflow Limitation: Outcome Measures and Sample Size

Outcome Measures and Sample Size
The chronic respiratory disease questionnaire (CRQ), 6-min walk, FEV1, and FVC were assessed at baseline, 6 months, and 12 months in both the n of 1 trial and standard practice groups. The CRQ is a valid, responsive, quality-of-life index specific for CAL that measures four domains. These domains can be combined into larger domains of Physical Function (combining dyspnea and fatigue) and Emotional Function (combining emotional function and mastery). The 6-min walk has been used to measure exercise capacity in several diseases, including irreversible CAL, and was administered with standardized encouragement. The items and response scale (dyspnea during up to five daily activities and a 7-point Likert response scale) comprising the CRQ dyspnea domain, as measured at baseline, 6 months, and 12 months, were identical to those used in the personalized daily patient diaries that were used by patients randomized to n of 1 trials, with three exceptions. First, the n of 1 trial patients did not complete the other three CRQ domains when completing their diaries during the n of 1 trials. Second, the reference time for dyspnea as measured in the n of 1 trials was the day that the diary was being completed (eg, “How short of breath were you today when you were climbing stairs?”) vs the preceding 2 weeks when completing the full CRQ at baseline, 6 months, and 12 months (eg, “Please indicate how much shortness of breath you have had in the last 2 weeks while climbing the stairs?”). Third, dypnea ratings during the n of 1 trials used patient self-report, whereas completion of the full CRQ was performed in the presence of a study nurse.
The recommendation within the first 3 months to continue or stop theophylline usage for all patients was recorded, as was the proportion of patients taking theophylline at 6 and 12 months. Patient and physician confidence in the treatment decisions were independently assessed by the question, “How confident are you that theophylline should be stopped?” or “. . . continued?,” with responses ranging from 1 (totally comfortable) to 7 (extremely uncomfortable). www.canadian-familypharmacy.com website Cointerventions (inhaled agents [beclametha-sone diproprionate, budesonide, flunisolide, P2-agonists, and ipratropium bromide], prednisone, and home oxygen) in the week before the 6- and 12-month assessments were also recorded.

Category: Airflow Limitation

Tags: irreversible chronic airflow limitations, n of 1 trials, randomized trial, theophylline