Self-rated physical health predicts change in disability in multiple sclerosis

Objective To examine whether self-rated physical health, as measured by the Physical Functioning Scale (PF) and the Role-physical Scale (RF) of the SF-36 Health Survey, could predict change in disability measured by the Expanded Disability Status Scale (EDSS) in patients with multiple sclerosis (MS) over a follow-up period of 3 years. Methods A group of 156 clinically definite MS patients (Poser criteria), who had never been treated with disease-modifying therapies, were recruited consecutively from an outpatient clinic setting at the Institute of Neurology, Belgrade. The self-rated physical health was measured by using PF and RF of the SF-36. Results At follow-up, 33 out of 156 patients (21%) had dropped out. The mean EDSS score had increased from 3.7 to 4.5. Multiple regression analyses using change in EDSS as the dependent variable and baseline scores of EDSS and RF as independent variables showed a significant effect for RF (standardized beta = -0.21). A similar but non-significant effect was found for PF. Dichotomizing change in disability according to clinically meaningful deterioration and using logistic regression, an odds ratio of 1.27 (95% confidence interval 1.01-1.62) was found for the smallest unit of change in the self-rated scale. This means that patients who rated their own physical health as poor had a higher increase in disability compared with patients with the same level of disability at baseline who rated their physical health better. Conclusions MS patients' perception of their health comprises information predictive for disease development not included in the more objective measure of disability status.