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We read the paper by Hankins et al in the recent BJGP with interest.1 We accept that published psychometric data concerning GPAQ is relatively limited, and are committed to further research and development of the questionnaire. However, the situation is as bleak as they make out.
Forms of validity such as face and content validity are an important aspect of questionnaire development, and GPAQ more than adequately meets these criteria. Hankins et al also failed to discuss four papers all of which include results from GPAQ or its precursor questionnaire GPAS.2–5 These are clearly relevant to the question of whether GPAQ is measuring important domains of patient satisfaction.
We agree with Hankins that validity testing is best done against an external criterion, but with a complex construct like patient satisfaction there is no obvious candidate criterion, and we note that Hankins et al do not suggest one either. In terms of predictive validity, the Primary Care Assessment Survey (PCAS), on which GPAQ is based, has been shown to predict patients' voluntary disenrollment from US primary care physicians.6 Hankins et al dismiss studies showing an association between GPAS scores and patient sociodemographic characteristics as evidence of validity. Formally they are correct, since there is a danger that such results demonstrate bias rather than validity. However, such results need to be considered in the context of the wider literature. As other validated questionnaires show associations between patient characteristics like increasing age and satisfaction score, and as there are theoretically cogent reasons why such associations would occur, then GPAS data demonstrating similar associations can be taken as evidence of validity
We feel that the authors' suggestion that ‘it is not clear that the questionnaires measure satisfaction at all’ is a serious overstatement that does not accurately reflect the considerable conceptual and empirical work that has been completed to date. That work was the basis for an independent group of academic advisors recommending that GPAQ and IPQ should be selected for use in the GP contract.