Assessment of Health-Related Quality of Life in Chronic Dialysis Patients with the COOP/WONCA Charts

Abstract

The aim of the present work was to determine the health-related quality of life (HRQOL) of our patients on hemodialysis using the COOP/WONCA charts. A further aim was to explore its psychometric characteristics. The present study included all patients attending the hemodialysis unit of our hospital. The comparative study of the results was conducted with other population groups in which this questionnaire has been applied previously (primary-care patients, their accompanying persons, pregnant women, Alzheimer patient carers and drug addicts). The dimensional structure of the questionnaire was explored by factorial analysis of principal components, and internal consistency was evaluated with the Cronbach alpha factor. Concurrent validity was determined by comparative analysis of the results of the COOP/WONCA charts with those of another questionnaire, the 36-item short form of the Quality of Life Score (SF-36). To do so, 60 randomly chosen patients completed both questionnaires. 98.9% of patients completed the COOP/WONCA charts in their entirety. The mean scores of all the charts, with the exception of overall health, are in the range of what could be called 'favorable area of quality of life' (below 3). With respect to the rest of the groups, the dialysis patients had the best scores on the 'feelings' and 'social activities' charts and none of the worst ones. The joint factorial analysis revealed that the questionnaire has a 3-factor structure: factor 1 or daily functioning, factor 2 or quality of life and health, factor 3 or the psychosocial factor. The Cronbach alpha value for the 9 charts was 0.766. All the correlations between equivalent dimensions of questionnaires COOP/WONCA and SF-36 were statistically significant (p < 0.01). The convergent validity mean was 0.57 and the discriminant validity mean was 0.22, appreciably lower than convergent validity. This study shows that the process of psychological adaptation to problems deriving from dialysis is satisfactory. Moreover, the COOP/WONCA charts are a useful instrument for the determination of the HRQOL in hemodialysis patients without losing psychometric quality.