Spanish validation of the telephone assessed Expanded Disability Status Scale and Patient Determined Disease Steps in people with multiple sclerosis

Background: The Expanded Disability Status Scale (EDSS) and Patient Determined Disease Steps (PDDS) are two of the most widely disability scales used in multiple sclerosis (MS). When physical visits are unavailable, remote evaluation through telephone interview may be helpful. We aimed to translate both scales into Spanish, and to 1) validate the telephone EDSS and PDDS, and 2) explore the association pattern between both telephone questionnaires. Methods: 103 patients underwent a neurological examination to generate the EDSS and completed the PDDS questionnaire. Telephone questionnaires (EDSS, PDDS) were performed within 15 days. Feasibility and psychometric properties of both telephone questionnaires included internal consistency, acceptability, inter-rater agreement and validity. Test-retest reliability was evaluated in 36 patients. Results: Both scales showed excellent internal consistency and test-retest reliability. The agreement between conventional and telephone assessments in ambulatory impaired patients (EDSS > 4.0) was good for EDSS (kappa = 0.72) and excellent for PDDS (kappa = 0.93); fully ambulatory patients (EDSS <= 4.0) showed lower values (kappa = 0.24, and 0.54, respectively). Full agreement was higher for telephone PDDS than telephone EDSS (78% vs 44%). Overestimation of disability was more frequent in fully ambulatory patients. Strong correlation was found between telephone questionnaires (rho = 0.88; p < 0.001). The pattern of association was not isomorphic, but a PDDS cut-off of 3 identified with high accuracy patients with ambulatory impairment. Discussion: Telephone EDSS and PDDS questionnaires for Spanish patients are valid tools to assess disability status in MS and offer complementary information. Patients with ambulatory impairment are those who benefit the most from a remote assessment.