Development and Validation of the Polish Version of Questionnaire for the Assessment of Psychosocial and Functional Effects of Metastatic Breast Cancer.

The aim of this study is to adapt culturally and validate a questionnaire assessing experiences of metastatic breast cancer (MBC) patients in Poland. The questionnaire development was divided into three phases: bidirectional translation of the survey, testing it for acceptability and relevance, and field testing. In the field study, 320 women with MBC completed the questionnaire, 50 of them twice for retest. Basic psychometric properties of the items used in questionnaire were analyzed. Test-retest reliability was assessed using kappa coefficient. In case of some items, known-group validity was verified. We made minor revisions to the construction and wording of the questionnaire. The analysis of the variables distributions used in the final version of the questionnaire showed that there were no redundant response categories across items. We checked for the floor and ceiling effect. It was found that there were a total of < 40% respondents selecting the lowest or the highest possible score. The observed values of the Kappa coefficients indicated high tool's stability. We compared predefined groups for known-group validity; few expected associations reached statistical significance, which supported the overall validity of the tool. The questionnaire has been successfully developed. The results confirm the validity, reliability, and applicability.