Abstract: Objective: To develop and assess the psychometric properties of the questionnaire of knowledge, attitude, and behavior on genetic risk for breast cancer in patients and their first-degree relatives. Methods: Based on the Knowledge-Attitude-Practice, the questionnaire of knowledge, attitude, and behavior on genetic risk for breast cancer in patients and their first-degree relatives was developed through literature review, semi-structured interviews, group discussions, two rounds of expert consultation and pilot survey. The psychometric properties of the questionnaire were assessed in 313 patients with breast cancer and their first-degree relatives who were recruited by convenience sampling. Results: The questionnaire involved 3 dimensions: knowledge, belief and behavior, with 34 items totally. The content validity index S-CVI/Ave was 0.969. The Cronbach's α was 0.872, the split half reliability was 0.720, the test-retest reliability was 0.905. Conclusion: The questionnaire of Knowledge-Attitude-Practice on genetic risk for breast cancer in patients and their first-degree relatives has good reliability and validity, and can be used to assess the knowledge, attitude and behavior of genetic risk for breast cancer in patients and their relatives.

Key words: hereditary breast cancer; Knowledge-Attitude-Practice; questionnaire preparation; reliability; validity