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Abstract

The Symbol Digit Modalities Test (SDMT) and Digit Vigilance Test (DVT), both well-recommended attention tests for schizophrenia, are measures of switching and sustained attention, respectively. The purpose of this study was to investigate the test–retest reliability of the two attention tests in schizophrenia. A rater administered both tests on 147 participants with schizophrenia twice at a 1-week interval. Test–retest reliability was determined through the calculation of the intra-class correlation (ICC) coefficient. We also carried out the Bland–Altman analysis, which include a scatter plot of the differences between test and retest against their mean. System biases were evaluated by use of a paired t-test. The ICC for the SDMT was 0.87 and that for the DVT was 0.83. The limits of agreement (LOAs) of the SDMT and DVT were 11.5 to −9.9 correct responses and 156.3 to −249.2 s, respectively. The mean difference scores of the SDMT and DVT were 1.5 (4.7% of the first session mean; p= .002) and −46.4 (7.6% of the first session mean; p< .001). The ICCs show that the SDMT and DVT are stable measures across assessment in different sessions in schizophrenia. However, the paired t-test indicates a practice effect, and the LOAs show large variations. Thus, the SDMT and DVT are reliable for a group of subjects but limited for individual subjects with schizophrenia in 1-week interval clinical trials.

Attention, Digit Vigilance Test, Disability evaluation, Reproducibility of results, Schizophrenia, Symbol Digit Modalities Test
© The Author 2011. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: [email protected].
Issue Section:
Original Empirical Articles
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