Use of the Asthma Control Questionnaire by the Asthma Clinical Research Network

To the Editors:

In our original report previously published in the European Respiratory Journal (ERJ) [1], the Asthma Clinical Research Network (ACRN) utilised an unauthorised modified version of the Asthma Control Questionnaire (ACQ)^# administered over the telephone to demonstrate that the severity of a cold measured within the first 2 days was a predictor of subsequent worsening of asthma control. We subsequently stated this fact in an Erratum published in ERJ [2], and planned to conduct studies that would determine the impact of our modifications on the interpretation of our study.

The modified ACQ utilised in our study was a six-item modified version of a validated shortened version of the ACQ [3]; a question was also added to the beginning to ask if the subject had experienced a cold in the past 14 days. To determine whether these modifications of the ACQ altered the conclusions of the manuscript, adult asthmatics (n=96) with a cold were randomly administered the original ACQ in the clinic and then either the original or the ACRN modified ACQ over the telephone. The concordance correlation coefficient between the in-clinic original ACQ and the telephone-administered original ACQ was 0.96 (95% CI 0.93–0.98). The concordance correlation coefficient between the in-clinic original ACQ and the telephone-administered modified ACQ was 0.97 (95% CI 0.95–0.98).

Given the high concordance correlation coefficients in this study, we conclude that the modifications to the ACQ did not alter our conclusion that the severity of a cold measured within the first 2 days was a unique predictor of subsequent worsening of asthma control. Furthermore, the telephone administration of the ACQ does not appear to alter the performance characteristics of this instrument. In the future, we will utilise the original version of the ACQ to assess post-cold asthma control.

• ©ERS 2011