Repeated assessment of neuropsychological deficits in multiple sclerosis using the Symbol Digit Modalities Test and the MS Neuropsychological Screening Questionnaire.

BACKGROUND: Brief cognitive performance tests and self-report measures of neuropsychological symptoms have been proposed for screening purposes in multiple sclerosis (MS) clinics. To better understand the reliability of screening methods, two tests, the Symbol Digit Modalities Test (SDMT) and the MS Neuropsychological Screening Questionnaire (MSNQ), were administered to 76 patients with MS and 25 healthy controls, matched on demographic characteristics.
METHODS: Tests were administered at monthly intervals, over 6 months. In addition, the Beck Depression Inventory Fast Screen for medical patients (BDIFS) was administered to monitor for changes in depression. Our objectives were to determine the reliability of these measures and the relative contribution of cognitive impairment and depression in predicting self-report MSNQ scores.
RESULTS: Results showed that both the SDMT and MSNQ have good to excellent reproducibility over repeated testing. In MS, there are minimal practice effects over successive tests, in the order of 0.2 SD for SDMT and minimal change in the MSNQ. Regression analyses modeled to predict MSNQ based on SDMT and BDIFS showed significant contribution for both, but with the majority of variance being accounted for depression.
CONCLUSIONS: We conclude that these brief screening tests provide some independent information about the mental status of patients with MS and are reliable, even when used in monthly, successive examinations.