RESUMEN
Health professionals working in services providing genetic counseling need objective instruments to assess genetic counseling outcomes and also to "give a voice" to those using these services. Lack of knowledge regarding such outcomes may directly impact the effectiveness and the potential benefits of counseling, quality of life, health promotion, and empowerment of those receiving counseling. There are very few instruments available for most countries, however there are none in Brazil. In this context, this study aimed to adapt and preliminarily validate the Genetic Counseling Outcome Scale (GCOS-24), a Patient-Reported Outcome Measure (PROM), originally developed in British English. This methodological study recruited 278 individuals attending a medical genetic service at a Brazilian university hospital. We performed the translation, back-translation, semantic validation, pilot study and field study for testing of some psychometric properties. The instrument's internal consistency and test-retest reliability (stability) were assessed using Cronbach's alpha coefficient and Intraclass Correlation Coefficient, respectively. The Brazilian version of the GCOS-24 presented face and content validity, satisfactory internal consistency (Cronbach's α = 0.71), and moderate stability (ICC = 0.52). It was considered reliable, easily understood and relevant to assessing the genetic counseling outcomes for the study participants. Its construct validity still needs to be assessed to verify the instrument's internal structure and its potential use to measure change in empowerment following genetic counseling provided by Brazilian clinical genetics services.