Inclusion of the Symbol Digit Modalities Test in a revised assessment of 'no evidence of disease activity-4 (NEDA-4)' in Latin-American patients with multiple sclerosis.

Background: In relapsing-remitting multiple sclerosis (RRMS), no evidence of disease activity-3 (NEDA-3) is defined as the absence of: (1) relapses; (2) disability progression; (3) MRI activity (new/enlarged T2 lesions and/or gadolinium-enhanced T1 lesions). NEDA-4 status is defined as meeting all NEDA-3 criteria plus having an annualized percentage brain volume change (a-PBVC) >-0.4%. In individual patients, brain volume assessment is confounded with normal aging, methodological limitations and fluid-shift related fluctuations in brain volume. Cognitive impairment has been proposed as another component that should be integrated into therapeutic algorithms for RRMS. We aim to determine the proportion of patients failing to meet NEDA-4 criteria and to appraise whether the Symbol Digit Modalities Test (SDMT) is capable of replacing a-PBVC as one of the components of NEDA-4. We hypothesize that NEDA-4 has the potential to capture the impact of DMT therapies in RRMS.

Methods: Forty-five patients were prospectively followed 1 and 2 years after their baseline assessment at the University of Chile Hospital. SIENA software was used to assess a-PBVC.

Results: At baseline, the patients had a mean age of 33.0 years (range 18-57), disease duration of 1.9 years (0.4-4), Expanded Disability Status Scale score of 1.3 (0-4), and 67% were female. The majority had RRMS (91% while 9% had clinically isolated syndrome (CIS)). Seventy-three percent were on the so-called first line DMTs such as interferons (53%), glatiramer acetate (13%), teriflunomide (9%), and 18% were on fingolimod. There was a serial decline in the proportion of NEDA: after 1 and 2 years of follow-up 60% and 47% met NEDA-3 status, and 38% and 27% met NEDA-4, respectively. At the last follow-up 21% remained on interferons, 47% were now on fingolimod, 4% on alemtuzumab and 2% on natalizumab. At year 1 and year 2, with the replacement of a-PBVC by SDMT, 53% and 40% of patients achieved a putative NEDA-4 status, respectively.

Conclusion: Brain volumetric MRI has yet to be translated into clinical practice and SDMT may qualify as the fourth component of NEDA-4 definition. NEDA-4 has the potential to capture the impact of DMT therapies in RRMS earlier in the disease course of RRMS.