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Background and PurposeInformation processing speed is one of the most impaired cognitive functions in multiple sclerosis (MS). There are two tests widely used for evaluating information processing speed: the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT). To analyze the relationship between processing speed and the clinical and social support variables of patients with MS.MethodsA group of 47 patients with relapsing-remitting MS was studied, 31 were women and 16, men. Age: 39.04±13.17, years of schooling: 13.00±3.87, Expanded Disability Status Scale (EDSS): 2.78±1.81, and disease evolution: 8.07±6.26. Instruments of measure; processing speed: SDMT, PASAT, clinical variables: EDSS, Fatigue Severity Scale (FSS), Beck's Depression Inventory II (BDI-II), and social support: Medical Outcomes Study Social Support Survey (MOS).ResultsSignificant correlations were found between information processing speed and psychiatric, motor disability and social support variables. The SDMT correlated significantly and negatively with BDI-II, FSS, EDSS, and MOS (p<0.05), whereas the PASAT correlated negatively with FSS and positively with MOS (p<0.05). Information processing speed appeared as the performance predictor of these variables. The SDMT produced significant changes in EDSS (R2=0.343, p=0.000); FSS (R2=0.109, p=0.031); BDI-II (R2=0.124, p=0.018), and MOS (R2=between 0.212 and 0.379, p<0.05).ConclusionsInformation processing speed has influence on the clinical variables and the social support of patients with MS. These aspects are important to bear in mind for therapeutic approach.

The aim of this study was to standardize the Symbol Digit Modalities Test (SDMT)-Oral version in a healthy population living in Argentina and to analyze the influence that age, gender, and education have on the SDMT. Secondarily, it is intended to analyze the performance of patients with multiple sclerosis (MS) on this test. Two hundred ninety-seven healthy participants were evaluated; they had an average age of 39.28 years and 13.87 years of schooling; 77.8% were women. The sample was segmented according to age in three groups: younger than 35 years old, 36 to 50 years old, and 51 to 70 years old. The sample was also segmented according to years of schooling in three groups: 11 years or less, 12 to 16 years, and more than 16 years. All participants were evaluated with the oral version of the SDMT. A clinical sample of 111 patients with MS was also assessed. The mean on the SDMT for the total sample was 51.34 (SD=12.76). The differences were significant between all groups, p<.05, according to age. The participants with a higher level of education performed better than did those with moderate education and those with less schooling, p<.05. There was a significant difference between patients with MS and healthy controls, p<.01. The SDMT is influenced by age as well as by schooling, although not by gender. The norms displayed here will be useful to accurately evaluate the yield of the patients in the neuropsychological clinic when comparing them with their group of reference. It was also demonstrated that the SDMT can discriminate between patients with MS and healthy people.

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