Archive for the ‘Airflow Limitation’ Category


This finding supports the presence of an overall bias toward false conclusions of efficacy when stopping theophylline openly in patients with CAL who have been taking it for some time, and it provides justification to use n of 1 trials in this setting. However, this conclusion must be qualified because it is based on a post hoc analysis for which confirmation is needed.
Our study neither strengthens nor diminishes the case for considering a trial of theophylline in some patients with irreversible CAL. In particular, our overall negative result does not mean that theophylline should be abandoned because it is ineffective in all such patients. This is because 7 of 34 patients (21%) undergoing n of 1 trials demonstrated a potentially useful response to the drug on the basis of their daily dyspnea scores (Table 4). (more…)

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  • Theophylline for Irreversible Chronic Airflow Limitation: OutcomeOur secondary hypothesis that n of 1 trials would lead to less theophylline use than standard practice was also not confirmed in the present study. It was based on the premise that, overall, the biases of single-patient open trials favor false conclusions that the treatment is effective, and our previous randomized study of 26 patients in which 47% (95% CLs, 14%, 80%) fewer n of 1 trial patients than standard practice patients were taking theophylline at 6 months without differences in CRQ scores and the 6-min walk. Patients in our previous study had been on theophylline at the time of recruitment for at least a year, making them more comparable to prior-theophylline-use patients in the present study. (more…)

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  • This tendency toward low power is accentuated by the recommendation, to which we adhered, of excluding patients who were sure that theophylline was helpful following an open trial. However, our rate of stopping one half of the n of 1 trials before completing at least three treatment pairs is consistent with other studies, and it suggests that the failure of patients to complete multiple treatment crossovers is an inherent limitation of n of 1 trials. Our decision to exclude patients who were sure that theophylline was helpful following open therapy should not have invalidated conclusions regarding the effects of n of 1 trials or standard practice on group outcomes because of differing baseline perceptions about the drug’s value. This conclusion is based on our randomizing patients to n of 1 trials or standard practice only after confirming that they were uncertain about the effects of theophylline. However, this approach does limit the generalizability of our findings. Specifically, we did not assess the impact of initiating theophylline by either n of 1 trials or standard practice, and without an open run-in, in patients with CAL. (more…)

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  • Theophylline for Irreversible Chronic Airflow Limitation: DiscussionWe doubt that biased assessment of quality of life and exercise capacity explains our negative result. Personnel ascertaining these measures were masked to treatment- group allocation. We also suspect that the isolated finding of a higher CRQ Emotional Function score at 6 months among n of 1 trial patients within the No Prior Theophylline Use subgroup reflected chance. Thus, other reasons for our negative finding, beyond the main explanation that n of 1 trials are not effective in this setting, should be considered. (more…)

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  • Post Hoc Analysis Combining This Study and Our Previous Study
    Our previous study also randomized patients with irreversible CAL to guide theophylline therapy by n of 1 trials or standard practice. However, that study was limited to patients taking theophylline at the time of recruitment into the study, making them most comparable to prior-theophylline-use patients in the present study, and follow-up went only to 6 months. Therefore, we combined prior-theophyl-line-use patients in the present study with patients from our previous study (N = 61) and assessed their responses over 6 months. (more…)

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  • Theophylline for Irreversible Chronic Airflow Limitation: Conduct and Results of n of 1 TrialsConduct and Results of n of 1 Trials
    Four n of 1 trial patients stopped their n of 1 trials before or on completion of the first treatment period and refused to continue. Of these, three patients in the prior-theophylline-use group chose to remain on theophylline openly (two patients had received theophylline only and one patient had received placebo only), and one patient in the no-prior-theophylline-use group had received theophylline only and chose not to continue the drug. Of the remaining 30 patients, 4 provided diary scores for one pair of theophylline and placebo treatments from which a point estimate on the difference in dyspnea score could be determined. The other 26 patients completed at least two treatment pairs (8 patients, two pairs; 6 patients, three pairs; 12 patients, four pairs) from which CLs on the point estimate could also be determined. Early crossovers to alternate treatments within pairs occurred in six patients, and four patients were treated for a respiratory infection during the n of 1 trials but did not crossover or end the treatment period early. (more…)

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  • The confidence of physicians and patients in treatment decisions about theophylline use did not differ, whether the decision was based on an n of 1 trial or on standard practice (median confidence level in decision for physicians,  [range, 1 to 4]; median confidence level in decision for patients, 2 [range, 1 to 6]). The confidence level of physicians was slightly higher following the n of 1 trial (median, 2; range, 1 to 4) than following standard practice (median, 3; range, 1 to 4). The confidence level of patients also was higher following the n of 1 trial (median, 2; range, 1 to 6) than following standard practice (median, 2.5; range, 1 to 6). However, these differences were not significant. (more…)

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  • Theophylline for Irreversible Chronic Airflow Limitation: ResultsComparsion of All n of 1 Trial Patients to All Standard Practice Patients (Primary Analysis)
    Table 2 shows the CRQ scores, 6-min walk results, and spirometry values over time. No significant differences between the n of 1 trial patients and standard practice patients were seen in changes from baseline in these outcomes at 6 and 12 months. The 95% CLs for the between-group differences (n of 1 trial minus standard patients) in within-group changes over time (12 months minus baseline) in the CRQ Physical Function score, CRQ Emotional Function score, and 6-min walk were, respectively: -8.2, 2.5; -4.7, 5.7; and -26, 42 m). (more…)

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