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The use of health status as an outcome measure in chronic obstructive pulmonary disease (COPD) is becoming more popular. We therefore welcome the publication of information which improves the choice of appropriate questionnaire. The recent paper by Rutten-van Mölken and colleagues could have made an important contribution to this area.1 However, we are seriously concerned about the validity of their comparison between the St George's Questionnaire (SGRQ) and the Chronic Respiratory Questionnaire (CRQ).
The clinical usefulness of the CRQ is limited because it is interviewer led while the SGRQ is self-administered. The development of a validated self-administered version of the CRQ would be a major advantage for clinical trials and clinical practice. The authors give the impression that a validated self-administered version of the CRQ already exists and have used this in their study. However, such a version is not described in the original reference as claimed and has never been disseminated by publication.2
We have recently been working with the original authors of the CRQ to develop and validate a self-reported CRQ and the results have so far only been published in abstract form.3 ,4 We therefore believe that the results described in the paper are devalued by the misleading implication that a self-report version of the CRQ has been correctly developed.
author's reply Validation of a quality of life questionnaire needs to be an ongoing process because the measurement properties of a questionnaire may vary depending on the population and the context in which it is used. Our paper, in which we compare the self-reported CRQ and SGRQ, is a contribution to the validation of the self-reported version of the CRQ. Williams and colleagues have made a head to head comparison of the self-reported and interviewer led versions of the CRQ, which is also an important contribution to the validation process.
We did not develop the Dutch self-reported version of the CRQ. We have used the Dutch self-reported version of the CRQ, which has been on the market for several years and is mainly used in studies initiated by the industry. To avoid confusion and enhance the comparability of the results we decided it was better to use this existing version than to develop yet another version of the same instrument.
The response of Williams and colleagues may give the impression that there are big differences between the self-reported and interviewer led Dutch versions of the CRQ. This impression is wrong. The phrasing of the questions in the self-reported version is exactly the same as in the interviewer led version. The dyspnoea domain is still “individualised”. The response options are also exactly the same. The only difference is that they are printed behind the questions instead of on separate cards.
I would suggest that the information of the various validation studies should be brought together so that the developers of the original CRQ can decide on one standard version of the self-reported questionnaire.