RESUMEN
The aim of the study was to assess a Spanish adaptation of a method that determines the categorical capacity status of potential participants in research projects. The sample consisted of 120 subjects (40 general medicine inpatients, 40 psychiatric inpatients, and 40 healthy controls). The MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR) interview and Mini-Mental State Examination (MMSE) were used. A feasibility study was carried out and reliability and validity calculations were made against the expert-judgment gold standard. The mean duration of the MacCAT-CR was 13 min. For the MacCAT-CR understanding, appreciation, reasoning, and expressing a choice subscales, the intraclass coefficient correlation (interrater reliability) was .93, .88, .90, and .50, respectively, and internal consistency (Cronbach's alpha) was .96, .94, and .95, respectively. Patients considered to be incompetent for expert-judgment obtained lower scores in the MacCAT-CR interview. The Spanish version of the MacCAT-CR is feasible, reliable, and valid for assessing the capacity of patients to give consent in research.