Development of Willingness-to-Pay Questionnaire on Health Insurance Cost-Sharing for Catastrophic Prescription Drugs: A Content Validity and Reliability Assessment

Prescription drug cost -sharing in Indonesia remains challenging because no valid willingness -to -pay (WTP) questionnaire on cost -sharing is available. This study aimed to conduct an item selection and assess the content validity of a WTP questionnaire for prescription drug cost -sharing under the national health insurance scheme in patients suffering from catastrophic illnesses. The method was a cross-sectional study and used a four -step design, including study development, content validity, response process, and reliability. This research involved nine experts, including professionals, academics, and pharmacy experts in hospitals, to validate the content of a WTP questionnaire for prescription drug cost -sharing. The questionnaire items were extracted from many sources, such as cost analysis of catastrophic prescription drug data in Indonesia and reviews of articles with the terms ``willingness -to -pay,'' ``cost -sharing,'' ``health insurance,'' ``prescription,'' and ``questionnaire.'' This content validity study used the content validity index (CVI) and content validity ratio (CVR) for both the individual item measurement and the overall scale. The Pearson correlation was assessed for the test-retest reliability. A draft questionnaire of 47 items was developed with four domains: healthcare utilization information, participation in health insurance information, drug information, and costsharing scenarios. Three items were removed, and three were merged based on the content validity study. The overall scale of the questionnaire was good with 0.94 S-CVI/Ave. The test-retest reliability coefficient had a strong correlation (r = 0.98). We conclude that the WTP questionnaire for prescription drug cost -sharing had been developed and validated through evidence validity, including content validity (CVI and CVR), response process, and reliability. As a follow-up, a new 42 -item questionnaire was developed.