[Development of a questionnaire to measure asthmatic patients' knowledge of their disease]

To develop a valid, reliable, and sensitive self-administered questionnaire in Spanish to measure the knowledge asthmatic patients have of their disease.

The face and content validity of the questions was established by consensus among expert pulmonologists. To determine the importance of the questions, they were put to 100 participating asthmatic patients. The number of questions was reduced by consensus taking into account the importance given to each question by these patients. A further 25 patients participated in the assessment of reliability and sensitivity. The questionnaire was administered 5 times: twice before and 3 times after an educational intervention. The direct and indirect external consistency (kappa statistic) and the overall kappa value were determined. Sensitivity was assessed from the number of correct answers before and after the intervention (Wilcoxon test; P< .05) and from the percentage change (>40% was clinically significant).

Fifty-nine questions were drawn up and the final version included 20. The test-retest consistency was between 0.81 and 1 in 76% of the cases before the intervention and in 92% after it. The kappa statistic before the intervention was between 0.41 and 1 in 96% of the cases, and between 0.81 and 1 in 88% afterwards. The overall kappa values before and after the intervention were 0.12 and 0.43, respectively. The median sensitivity, measured as percentage change, was 67% and 10 patients showed an improvement between 81% and 233%.

The questionnaire is reliable, has face and content validity, and is very sensitive to change. In view of these results, this instrument is useful for measuring the knowledge that asthmatic patients have of their disease in clinical practice and investigation.