Comparison of respiratory symptoms questionnaires

SETTING: Comparisons in performance of questionnaires are of interest in in ternational comparisons of prevalences and risk factors, after translation and development of new questionnaires. Factors such as sex, age, educationa l level and smoking habits may influence the performance of questionnaires. OBJECTIVE: 1) To discuss questionnaire comparisons in general, using as an example a Norwegian respiratory symptoms questionnaire compared with a tran slation of the British Medical Research Council questionnaire on chronic br onchitis; and 2) to examine whether reliability differs in subgroups, DESIGN: A population sample of 935 residents of Hordaland County, Norway, c ompleted two questionnaires in a short interval of time. Agreement and Cohe n's kappa were calculated. RESULTS: Prevalences were significantly differen t between the two questionnaires for most symptoms. Agreement decreased fro m non-smelters through ex-smokers to smokers, whereas the kappa statistic i ncreased. Agreement increased as the educational level increased, whereas t he kappa statistic declined, No significant age and sex effects on agreemen t and kappa were observed. CONCLUSION: Small changes in the phrasing of a question can have considerab le effect on prevalence estimates. Reliability statistics are prevalence de pendent, Reliability may differ according to smoking habit and educational level. Questionnaires should be tested in the population that they are to b e used in.