EDSS Accuracy Heightened by Including SDMT and FSS for Those With Multiple Sclerosis

Sarah A. Morrow, MD, FRCPC, MS

The accuracy of the Expanded Disability Status Score (EDSS) may be increased when cognitive changes during relapse activity are factored in from the Symbol Digit Modalities Test (SDMT) and the Fatigue Severity Score (FSS), according to results from a prospective study.

Lead author Sarah A. Morrow, MD, FRCPC, MS, professor of neurology, Western University, and colleagues incorporated the SDMT into the cerebral Functional System Score (CFSS) of the EDSS in a cohort of 592 persons with multiple sclerosis (MS). The main outcomes were a modified CFSS (m-CFSS) and modified EDSS (m-EDSS), incorporating SDMT and FSS in each patient and accounting for cognitive performance and fatigue rating during relapse.

They found that the m-CFSS was significantly higher than CFSS at baseline (median, 2 vs median, 0; P <.001) and relapse (median, 2 vs median, 1; P <.001). Additionally, the m-EDSS was higher than EDSS (median, 3.0 vs median, 2.5; P = .02) at relapse, including 35 patients (43.8%) in the relapse group (RG) who had higher m-EDSS than EDSS at relapse.

Morrow et al noted, “It is hoped that these findings will lead to further improvement in the clinical detection of relapses and cognitive change over time which can improve our ability to treat and support our MS patients.”

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Among the full cohort, 80 persons with MS qualified for RG and 72 were matched to the stable group (SG). Participants from both groups underwent the same evaluation at relapse and 3 months later in an effort to improve the accuracy of EDSS and detecting cognitive changes.

In total, 40% of relapsing subjects had higher scores on the m-CFSS than the CFSS at the relapse timepoint due to the incorporation of the SDMT scores. Furthermore, 21.3% of relapsing subjects saw increases in scores because of FSS scores, and 6.3% because of both SDMT and FSS contributions.

At relapse, 32.5% of the cohort did not report higher m-CFSS than CFSS. From baseline to relapse, there was no significant longitudinal change in CFSS (P >.05). However, there was a significant increase in m-CFSS from baseline to relapse (P = .014). A closer examination showed 10 more subjects who increased from baseline to relapse assessments on m-CFSS (n = 27; 33.8%) than on CFSS (n = 17; 21.3%).

T2 lesion volume (T2LV), determined on the T2-FLAIR sequence, correlated significantly with the m-CFSS (r = 0.532; P <.001) but not with the CFSS (r = 0.200; P >.05) at the relapse timepoint.

Investigators found no correlation between the gadolinium enhancing (Gd+) lesion volume at relapse between m-CFSS (r = 0.08; P = .53) or CFSS (r = –0.16; P = .20). Despite being non-significant, the was a trend in the difference of the mean Gd+ lesion volume in those who had an increase in m-CFSS only compared to the rest of the subjects (m-CFSS increase only group, 0.420 mL [standard deviation (SD), 0.509]; remaining subjects, 0.226 mL [SD, 0.431]; t = 1.8062; df = 22.226; P = .08).

A sub-analysis that examined employment revealed that scores on the m-CFSS were significantly associated with employment status at baseline (employed vs unemployed estimate, –1.09; P <.001).

"A future project could examine the sensitivity and specificity of the EDSS versus the m-EDSS in identifying relapses in persons with MS, as well as the utility of including the SDMT in the m-EDSS to aid in detecting progressive cognitive changes independent of relapse activity,” Morrow et al concluded.

REFERENCE

Morrow SA, Conway D, Fuchs T, et al. Quantifying cognition and fatigue to enhance the sensitivity of the EDSS during relapses. Mult Scler J. Published online December 1, 2020. doi: 10.1177/1352458520973618