Reliability, validity, and sensitivity testing of the expanded prostate index composite—Filipino version

Abstract

Objectives The expanded prostate index composite (EPIC) is a widely used and well-validated quality of life (QOL) tool for prostate cancer patients. We developed a filipino version (EPIC-F) and tested its psychometric properties. Material and Methods The EPIC-F and validated filipino versions of the international prostate symptoms score (IPSS), international index of erectile function-5 (IIEF-5), and european organisation for research and treatment of cancer (EORTC) prostate cancer module (PR-25) were administered to patients with nonmetastatic prostate cancer at baseline, 10–14 days later and after ≥15 radiotherapy (RT) sessions. Cronbach’s α, pearson correlation, and linear regression were used for reliability, validity, and sensitivity analyses. Alpha was set at p < 0.05. Results The validation cohort comprised 52 patients aged 54–86 years (70.10 ± 6.9), with stage I (21%), II (27%), III (33%), or IVA (19%) disease. At enrolment, 38% had prior surgery; 19% had prior RT and 81% were to undergo RT; and 31% were on hormonotherapy. Internal consistency was good to very good for all domains (Cronbach’s α, 0.783–0.866). Test-retest reliability was moderate for all domains (Pearson’s r, 0.509–0.688), except for the hormonal domain (low r, 0.369). Interscale correlation was moderate to high between each domain and its corresponding reference scale (r, 0.551–0.834), except between the bowel domain and the PR-25 bowel (low r, 0.457). Sensitivity testing showed a strong r2 (0.311) for the bowel domain, but weak for the rest. Conclusion The EPIC-F is a reliable, valid, and sensitive tool for assessing the QOL of filipino prostate cancer patients.