Construct Validity and Reliability of Indonesian Version of RAND SF-36 Quality of Life Questionnaire in Breast Cancer Patients

Abstract
Background: The number of breast cancer patients in Indonesia is increasing but there are still only a few researches that assess their quality of life. RAND SF-36 is a quality of life instrument that is widely used. In Indonesia, the validity and reliability of the instrument is still under development, especially in breast cancer patients. Various health status questionnaires have been used in physical rehabilitation studies involving patient with pacemaker, but for women with breast cancer, the usefulness of these questionnaires as measures of physical, mental, and social well-being has not been firmly established. Methods: A previously validated RAND SF-36 questionnaire in patients with pacemaker was given to 252 breast cancer survivor community members. We assessed the construct validity and the reliability by referring to its Pearson’s r table value and Cronbach’s α coefficient. Results: One hundred and fourteen breast cancer survivor community members participated and completed all 36 questions of the instrument between September- November 2018. Questions number 2, 28, and 35 showed lower Pearson’s r value (r0.1548 indicating that these questions were valid. Cronbach’s α coefficient >0.90 indicated good internal consistency. Conclusions: The Indonesian version of the SF-36 quality of life questionnaire is a suitable instrument and can be used for research in Indonesian breast cancer patients.