Health-related quality of life in dialysis patients. A report from an Italian study using the SF-36 Health Survey. DIA-QOL Group.

Abstract

Interest in measuring health-related quality of life (HRQoL) has increased together with an awareness that such humanistic outcomes require valid and reliable measures. In the last decade short, simple and multidimensional generic and disease-specific questionnaires have been developed. Among the several generic questionnaires available, the Short Form 36 Items Health Survey (SF-36) was translated and validated in several languages, and applied to different settings and diseases. Within the framework of a larger, prospective, multicentre study (DIA-QOL project) the SF-36 was administered to 304 patients to test its characteristics in terms of patient acceptability, and psychometric and clinical validity. Standard psychometric techniques were used to evaluate its validity in terms of convergence, divergence and internal consistency reliability (Cronbach's alpha). Correlations between clinical variables and HRQoL scores were performed to test the questionnaire's capability to capture differences across patients groups. Overall, the findings show that, in this sample, the SF-36's performance was very good. Acceptability was satisfactory, with a response rate higher than 80%. All the questionnaire scales met the psychometric standards suggested in terms of grouping and scaling assumptions. The internal reliability coefficients actually replicate the satisfactory findings reported previously for the original SF-36. In terms of the ability of the questionnaire scales to discriminate between groups expected to differ in a given health concept in relation to clinical variables, the results were also good. On average, females reported lower scores, the impact of ageing was more evident for physical scales. Diabetic patients score significantly worse on the physical function scale and patients with mental health problems score significantly lower on the mental health scale. No significant association was found with the index KtV, haemoglobin levels, body mass index, parathyroid hormone and type of dialysis. A strong association was indeed found between SF-36 scales measuring physical health concepts and the serum albumin level. This association held after adjusting for the confounding effect of age. Comparison of the health profile of the present sample with others from the US and UK and from a representative sample of the Italian general population highlights the potential of such questionnaire in dialysis setting. The SF-36 questionnaire is easy to use in Italian dialysis patients and SF-36 scores are related to important clinical aspects. This approach can help in caring for dialysis patients and can be useful in outcome assessment programmes.