[Validation of a questionnaire to assess patient knowledge of their medicines]

Abstract

Objective: Patient knowledge of their medicines is closely associated to a better rational use of drugs, thus achieving better health outcomes from their use. The objective of this study is to design and validate a questionnaire to assess the level of knowledge patients have about their medicines.

Design: (A) Questionnaire: Literature review, some qualitative techniques (expert panel, brainstorming, Delphi method) and some pilot studies. (B) Questionnaire validation.

Setting: A community pharmacy in the city of Malaga.

Participants: Patients attending the selected pharmacy, asking for at least one medicine.

Main measurements: The discriminant capacity of the items was assessed. Content and construct validity were analysed using the Spearman's Rho coefficient and Factor Analysis method. Reliability was assessed by measuring internal consistency, equivalence (inter-observer concordance) and test-retest reliability.

Results: The final questionnaire, with 11 items explaining the different dimensions of knowledge found, was completed by 102 patients (a response rate of 95.3%) with a mean age of 46.6 years (SD 16.70). Mean time to complete it was 4.9 min (SD 2.2). Factor analysis showed a probable structure of 4 factors explaining the 67% of the total variance. The Spearman-Brown Rho coefficient was 0.30 (p<0.05). Cronbach alpha was 0.677, Kappa's coefficient=0.99 and intra-class correlation coefficient=0.745 (95% CI: 0.49-0.87).

Conclusions: The designed questionnaire is dynamic, valid and reliable, being able to measure the level of patient knowledge on the medicines they use.