Validity and Reliability of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 – Tagalog among Adult Filipinos with Differentiated Thyroid Cancer

OBJECTIVE: This study aims to determine the convergent and discriminant validity and internal consistent reliability of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) Tagalog among adult Filipinos with differentiated thyroid cancer (DTC). METHODOLOGY: 104 adult Filipinos with DTC at various disease stages self-administered the EORTC QLQ-C30 version 3 Tagalog and Short Form-36 (SF-36) version 2 Tagalog. Concurrent validity between conceptually-related scales from both tools was determined. Convergent and discriminant validity of multi-item scales of the EORTC QLQ-C30 Tagalog were assessed by Spearman’s correlation. Cronbach's α was computed. RESULTS: The EORTC QLQ-C30 Tagalog showed moderate correlation with similar scales in the SF-36 Tagalog particulary for physical, role and social functioning, pain, and global health (r=0.42-0.48, p<0.001). It showed satisfactory item-domain convergent and discriminant validity for all scales except pain, fatigue, physical and cognitive functioning. Internal consistent reliability was good with cronbachs α ranging from 0.77 to 0.88 for global health, emotional and role functioning and symptom scale of nausea/vomiting. CONCLUSION: The EORTC QLQ-C30 Tagalog had acceptable convergent and discriminant validity and internal consistent reliability for the scales of global health, role, social and emotional functioning and nausea/vomiting when applied among adult Filipinos with DTC.