Self-administration and standardisation of the chronic respiratory questionnaire: a randomised trial in three German-speaking countries

The chronic respiratory questionnaire (CRQ) has demonstrated excellent measurement properties in patients with chronic obstructive pulmonary disease (COPD), but in its original form it is limited by the requirement for interviewer-administration and the individualised dyspnoea questions. The objective of this randomised trial was to examine the evaluative properties of the interviewer and self-administered German CRQ as well as of a standardised CRQ dyspnoea domain. In a multinational trial we randomly allocated 71 patients with COPD to complete the interviewer administered CRQ (CRQ-IA) or the self-administered CRQ (CRQ-SA) and other validation measures at the beginning and end of a respiratory rehabilitation program. We assessed and compared responsiveness and longitudinal validity of the CRQ. The change scores of all CRQ domains were above the minimal clinically important difference of 0.5. Responsiveness of the fatigue domain was higher for the CRQ-SA compared to CRQ-IA (P = 0.02), but there was no difference in responsiveness on the other domains. Compared to the standardised dyspnoea domain the individualised dyspnoea questions tended to show greater responsiveness for both the CRQ-IA (P = 0.07) and CRQ-SA (P = 0.10). We found better longitudinal validity for the CRQ-SA represented by larger correlations between CRQ change scores and those of other validation instruments. Taken these results into consideration, researchers in COPD, in particular those in German-language countries can utilise any one of four CRQ formats that have proved both valid and responsive.