Evaluation of Psychometric Quality of EQ-5D-5L Scale for Assessing Health-Related Quality of Life of Malaria Patients

OBJECTIVES: To evaluate the validity and reliability of the 5-level EuroQol 5-dimensional questionnaire (EQ-5D-5L) through classical test theory and the Rasch measurement model.

METHODS: Three hundred patients treated for uncomplicated malaria in selected primary healthcare facilities of Plateau state, Nigeria, completed the EQ-5D-5L scale. Classical test theory was used to establish validity and Cronbach's alpha reliability of the scale. Rasch analysis was used to confirm the unidimensionality, item fitness, item and person separations and reliabilities, and targeting of item difficulty to patient ability levels and presentation on Wright map (item-person map).

RESULTS: The outcome of classical test theory revealed unidimensional scale with average variance extracted values > 0.5, and the square root of the average variance extracted for construct was greater than the correlation coefficients, indicating convergent and discriminant validities of the scale whose Cronbach's alpha coefficient (α) was 0.87. Rasch analysis indicated variance explained values of 88.3% and the eigenvalues of the first contrast was 1.3, further confirming the unidimensionality of the scale, whose fit index values were within accepted ranges. The high item and person separation and reliability values indicated the instrument's strength in detecting and evenly spreading items and persons on the Wright map based on item difficulty and the respondents' ability levels, respectively.

CONCLUSION: The EQ-5D-5L scale performed well in uncomplicated malaria, hence, it is recommended for use in the assessment of health-related quality of life in this patient population.