Improving screening for vascular cognitive impairment at three to six months after mild ischemic stroke and transient ischemic attack

Background: The Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) were compared with and without the addition of a brief processing speed test, the symbol digit modalities test (SDMT), for vascular cognitive impairment (VCI) screening at three to six months after stroke. Methods: Patients with ischemic stroke and transient ischemic attack were assessed with MoCA and MMSE, as well as a formal neuropsychological battery three to six months after stroke. VCI was defined by impairment in any cognitive domain on neuropsychological testing. The area under the receiver operating characteristic curve (AUC) was used to compare test discriminatory ability. Results: One hundred and eighty-nine patients out of 327 (58%) had VCI, of whom 180 (95%) had vascular mild cognitive impairment (VaMCI), and nine (5%) had dementia. The overall AUCs of the MoCA and MMSE scores and performance at their respective cut-off points were equivalent in detecting VCI (AUCs: 0.87 (95% CI 0.83-0.91) vs. 0.84 (95% CI 0.80-0.88), p = 0.13; cut-offs: MoCA (<= 23) vs. MMSE (<= 26), sensitivity: 0.78 vs. 0.71; specificity: 0.80 vs. 0.82; positive predictive value: 0.84 vs. 0.84; negative predictive value: 0.72 vs. 0.67; and correctly classified 78.6% vs. 75.5%; p = 0.42). The AUCs of MMSE and MoCA were improved significantly by the SDMT (AUCs: MMSE+SDMT 0.90 (95% CI 0.87-0.93), p <0.001; MoCA+SDMT 0.91 (95% CI 0.88-0.94), p < 0.02). Conclusions: The MoCA and MMSE are equivalent and moderately sensitive, and can be supplemented with the SDMT to improve their accuracy in VCI screening.