Development, validation and performance of a newly designed tool to evaluate functional medication literacy in Slovenia

Background Medication literacy refers to the ability of individuals to safely and appropriately access, understand and act on basic medication information. It is vital for correctly and safely using medications. General health literacy measures do not adequately address specific skills for medication literacy, and there are no general, self-administered, performance-based instruments for assessing patients’ medication literacy. Objective The aim was to develop and validate a self-administered performance-based questionnaire measuring functional medication literacy and to evaluate functional medication literacy among the Slovenian general population. Setting A random sample of adult Slovenian residents received the questionnaires at their home addresses. Method The initial content was derived from medication counselling literature. Thirteen patients and 14 healthcare professionals provided feedback about its comprehensibility, comprehensiveness, and difficulty thus supporting content and face validity. The developed questionnaire, comprising 30 items divided into 5 categories (dosage, adverse effects, interactions, precautions, and other information), was sent to a random sample of 1500 adult Slovenian residents. The overall validity of the questionnaire was assessed via reliability, criterion and discriminant validity using the Kuder–Richardson Formula 20, multiple linear regression and Mann–Whitney test. Descriptive statistics were used to evaluate medication literacy. Main outcome measure The psychometric properties of the questionnaire (reliability, content, face, criterion, and discriminant validity); level of functional medication literacy. Results A total of 402 residents returned eligible questionnaires (26.8% response rate). The Kuder–Richardson Formula 20 reliability coefficient for the whole questionnaire was 0.823. One item that did not demonstrate discriminant validity was deleted. Criterion validity was supported by a significant association between age and medication literacy (β = − 0.303). Income (β = 0.243) and current self-perceived health (β = 0.187) also were associated with medication literacy. The median of medication literacy score was 24 out of 29 points. Dosage-related items requiring understanding of long text instructions and the use of numeracy skills received the most incorrect answers. Conclusion A performance-based questionnaire measuring functional medication literacy among a general population with supported validity was developed. Slovenian residents encountered difficulties when dealing with items requiring prose literacy and numeracy skills, especially related to dosing. Special attention should be paid to low-income elderly with poor self-perceived health.