Psychometric properties of the Brazilian version of the Female Sexual Function Index in women with breast cancer

Objective: to evaluate the measurement properties of the Female Sexual Function Index – Brazilian version in women with breast cancer. Methods: this methodological study involved 246 patients treated at two specialized breast cancer outpatient clinics. Data were collected using two instruments: a sociodemographic and clinical characterization questionnaire and the Brazilian version of the FSFI. Construct validity was assessed through confirmatory factor analysis, and reliability was evaluated using composite reliability. Results: in the factor analysis, the model achieved satisfactory results with acceptable fit indices (p=0.270; χ²/df=1.070; Comparative Fit Index=0.999; Tucker-Lewis Index=0.999; Standardized Root Mean Residual=0.061; Root Mean Square Error of Approximation=0.019). Evidence of reliability was also confirmed (composite reliability: 0.980). Conclusion: the instrument demonstrated satisfactory validity and reliability for assessing sexual function in women with breast cancer. Contributions to practice: this study provides methodological support for using this tool to assist in the nursing diagnosis of "Sexual dysfunction" in women with breast cancer.