Evaluation of disability, incapacity and environmental status scales in multiple sclerosis

From the Danish Multiple Sclerosis (MS) population a representative sample of 249 patients with a clinically definite diagnosis of MS has been tested by use of the Functional System Scale and Disability Status Scale of Kurtzke and the Incapacity and Environmental Status Scales of the IFMSS. Validity and reliability of the items and the properties of summed scales have been estimated. A statistical evaluation showed that generally the Incapacity and the Environmental Status Scales worked well. Problems encountered with the use of the Incapacity scale are mentioned and on statistical grounds a proposal of an incapacity scale with fewer items is presented.