Background: Cognitive decline is one of the most remarkable features of Multiple Sclerosis (MS) and particularly in pediatric onset MS (POMS). The Simbol Digit Modalities Test (SDMT), a simple, brief measure of information processing speed (IPS) has been proposed and it is increasingly used to explore cognitive functions in MS clinical trials. Recently a 4-point worsening on the SDMT score has been demonstrated to significantly correlate with a clinically meaningful cognitive decline.
Methods: The primary objective of this post-hoc analysis of a randomised computer-assisted rehabilitation trial for attention impairment in POMS was to test the clinical meaningfulness of the changes of SDMT scores by applying a 4-point SDMT cut-off. POMS exposed to specific computer training (ST) and nonspecific training (nST) were compared. All analyses were post hoc and not pre-specified. To evaluate the clinical meaningfulness of longitudinal changes over time of the SDMT in the ST and nST groups we applied a categorization of the delta SDMT scores (delta SDMT: SDMT score at T1 – SDMT score at T0) as follow: between -3 and 3 = not clinically significant; ≤ - 4 = clinically significant worsening; ≥ 4 = clinically significant improvement. The proportion of patients reporting a clinically significant SMDT improvement were compared between the 2 groups by using the chi-square test.
Results: Twenty-five % of POMS reported no clinically significant changes, 12.5% a clinically significant worsening and 62.5% patients a clinically significant improvement in the SDMT score at the end of the training program. The proportion of patients reporting a clinically significant improvement of the SDMT was significantly (p=0.008) higher (100%) in patients exposed to the ST in comparison to that (25%) in nST group.
Conclusions: In our RCT the use of the 4-point SDMT cut-off allows us to demonstrate the clinical meaningfulness of the results obtained by a home-based computerized program for retraining attention dysfunction in POMS patients with attention impairment. Further studies are needed to confirm the clinical validity of this cut-off and its applicability in the routine clinical practice setting