Background: To assess disease progression in multiple sclerosis (MS) several outcome measures are available. The interrelation of changes on different scales has not been studied extensively and the concept of combining scales has only recently been introduced in MS.
Objective: To explore combining different clinical outcome measures in the evaluation of disease progression in MS.
Methods: In 553 patients we studied the presence of relevant changes according to standard definitions on the Expanded Disability Status Scale (EDSS), Nine-Hole Peg Test (9HPT), Timed 25-Foot Walk (T25FW) and the Multiple Sclerosis Impact Scale (MSIS-29). We examined ‘exclusive worsening’ (worsening on one measure while not worsening on any other measure) and ‘opposing changes’ (worsening on one measure while improving on another measure). Finally, we investigated the impact of combining assessments.
Results: Based on the EDSS alone, 140 patients progressed. However, almost twice as many (275) showed worsening on any of the clinical outcome measures. Exclusive worsening was observed in 37 patients on the EDSS, 13 on the 9HPT, 39 on the T25FW and 44 on the MSIS physical. Of all worsened patients 76 (28%) showed opposing changes, a phenomenon predominantly observed when combining physician-based and patient-derived outcome measures.
Conclusion: When assessing disease progression in MS, sensitivity to change can be increased by combining different outcome measures. The added value is especially present when combining measures from different perspectives. However, further research is needed to evaluate the optimal way to combine outcome measures before implementing this strategy in clinical studies.
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