Neal S. Parikh, MD

Citing the high prevalence of cognitive impairment in patients with stroke, the authors call for better methods to easily detect cognitive impairment in this population. The authors aim to validate the Montreal Cognitive Assessment (MoCA) for classifying patients into three groups: low-, intermediate- and high-likelihood of moderate-severe cognitive impairment.

Three hundred and ninety patients referred to a stroke prevention clinic after stroke or TIA or other potentially cerebrovascular disease completed the MoCA. The mean age was 62 (range 17-94), and 53% were female. Patients were non-aphasic and English-speaking. Of the 390 patients, 34% had ischemic or hemorrhagic stroke, 34% had possible or probable TIA, and 32% had other vascular or non-vascular diagnoses (e.g. migraine). The gold standard for receiver operator characteristic/area under the curve analyses was an extensive neuropsychological battery.

The median MoCA score was 25 and did not differ significantly between diagnosis groups. By neuropsychological testing, 13% had moderate-severe cognitive impairment, and 30% had mild impairment.

Using a single cut-point for classification as moderate-severe impairment, test characteristics were optimal for MoCA <23 (sensitivity 60%, specificity 90%).

When two cut-points were assessed, the intermediate likelihood range was 23-27. In other words, a score of >27 reliably excluded patients with moderate-severe impairment (sensitivity 96%, negative predictive value 98%). A score of <23 reliably identified patients with moderate-severe impairment (specificity 90%, positive predictive value 49%). Of patients scoring in the intermediate likelihood range (23-27), 8% had moderate-severe impairment. The authors do not report the breakdown of the remaining 92% in terms of mild versus no cognitive impairment.

The MoCA may therefore help for identify patients unlikely to have cognitive impairment (e.g. “rule out”), but, as expected for a screening test, is not specific (e.g. not diagnostic). In their sample, 62% of patients fell into the intermediate group, and only 8% of these patients had moderate-severe cognitive impairment; this suggests that the intermediate range may not be a helpful category. However, for targeting assessments and interventions in clinical practice and research, the high specificity cut-point (MoCA<23) will certainly be of use.