EDSS Pyramidal Function Score Correlations with Objective and Subjective Measures of Ambulation

Background: Ambulation impairment limits daily activities and reduces quality of life for patients with multiple sclerosis (MS).  Patient-reported outcome (PRO) measures of limb functioning, getting up from a sofa and climbing stairs could provide efficient and reliable indicators of clinical status.  The Kurtzke EDSS pyramidal functional system score (PFSS) has been shown to detect disability progression in clinical trials.   

Objectives: To investigate the correlation between objective measures of ambulation by the EDSS-PFSS, Timed 25 foot walk (T25FW) and subjective measures by patient self-report.

Methods: A sample of 9,000 patients was extracted from the New York State Multiple Sclerosis (NYSMSC) consortium. Objective measures included EDSS as well as its PFSS, and T25FW.  Subjective measures were collected utilizing the validated LIFEware^SMPRO assessment for patients to self-report of  (1) lower limb limitation, (2) getting up from a chair, and (3) climbing stairs. Correlations were assessed using the Spearman rank correlation coefficient (r).

Results: Mean EDSS and PFSS scores were 3.5 (2.3) and 1.9 (1.5) respectively, while the average time to complete the T25FW was 30.2 seconds (57.8) respectively. Strong correlations were found between overall EDSS scores and self-reported lower limb functioning (r=.73, p<.001), getting up (r=-72, p<.001, and climbing stairs (r=-.73, p<.001), with slightly lower correlations found for PFSS scores and the subjective measures (r=.67 p<.001 for lower limb functioning, r=-.64, p<.001 for getting up, and r=-.65, p<.001 for climbing stairs). T25FW was also significantly correlated to all three subjective measures (r=.60, p<.001 for lower limb functioning, r=-.66, p<.001 for getting up, and r=-.64, p<.001 for climbing stairs).

Conclusions: High correlations demonstrate that EDSS detects ambulation disability similar to patients’ real-life experience.  Lower isolated PFSS correlations may be indicative of non-motor impairment contributions to ambulation limitation.  Results further underscore the value of PRO as a reliable and efficient tool in assessing disability and impact on activities of daily living.