Construct validity and reliability of EQ-5D-3L for stroke survivors in a lower middle income setting

Abstract

Introduction Stroke is a leading disease accounting for burden of chronic NCDs especially in lower and lower-middle income (LMI) settings. Quality of Life (QOL) is considered as an important facet of determination of success of patient management. EQ-5D-3L is a generic QOL tool. It provides an index score amalgamating responses for five descriptive questions and a visual analogue scale (VAS) value. Objectives To assess the validity and reliability of EQ-5D-3L for stroke patients in Sri Lanka, which is a LMI setting. Methods A descriptive cross sectional study was done among 100 stroke survivors among whom 50 each were managed at an ambulatory setting and an in-ward setting. A second wave of data collection was done for reliability analysis among one half of participants. The validity of EQ-5D-3L was assesses with five a-priori hypotheses. Reliability was assessed with test-retest method and with internal consistency. Non parametric Mann Whitney U test and Spearman correlation coefficients were used in the analysis. Results The EQ-5D index scores had significant positive correlation with SF-36 domain scores (p<0.001). The EQ-5D VAS scores had significant positive correlation with SF-36 domain scores (p<0.01). Index and VAS values of the EQ-5D were proved to be valid in known-group comparison (p<0.001). Participants reporting some kind of impairment for EQ-5D-3L dimensions had lower SF-36 domain scores. All the kappa values in the analysis of test-retest method were significant (p<0.001). For the VAS score, the Spearman correlation coefficient in test-reter analysis was 0.993 (p<0.001). Cronbach’s alpha value was 0.928. Conclusions and Recommendations EQ-5D-3L questionnaire demonstrates construct validity and a is a reliable toolin measuring QOL among stoke survivors in Sri Lanka.