Rosalind Lees1, Jane Lua2, Emily Melling2, Yen Miao2, Jia Tan2, Terence J Quinn3. 1. Institute of Cardiovascular and Medical Sciences, School of Medicine, University of Glasgow, Glasgow, UK. 2. Undergraduate Medical School, School of Medicine, University of Glasgow, Glasgow, UK. 3. Institute of Cardiovascular and Medical Sciences, School of Medicine, University of Glasgow, Glasgow, UK. Electronic address: Terry.quinn@glasgow.ac.uk.
Abstract
BACKGROUND: Guidelines recommend cognitive screening for all stroke survivors but do not suggest a preferred tool. Certain elements (orientation, executive function, language, and inattention) of the impairment scale, National Institutes of Health Stroke Scale (NIHSS), have been suggested as a short cognitive screening test-Cog-4. We aimed to describe accuracy and validity of Cog-4 against a more detailed cognitive assessment (Montreal Cognitive Assessment [MoCA]). METHODS: We assessed consecutive acute stroke unit admissions in 2 hospitals over 3 months. Four independent blinded assessors performed NIHSS and MoCA between days 1 and 4 poststroke. We described test properties of Cog-4 for MoCA-defined cognitive impairment using usual thresholds (Cog-4≥1 and MoCA<26 of 30) and described the correlations of individual Cog-4 components with broadly equivalent MoCA domains. RESULTS: We assessed 173 participants; 166 had Cog-4 data and 148 MoCA. MoCA described 84% (n=124) of assessed participants as having cognitive impairment and the Cog-4, 37% (n=62). Cog-4 had a sensitivity of .36 (95% confidence interval [CI]: .28-.45) and a specificity of .96 (95% CI: .80-.99) (positive predictive value: .98, negative predictive value: .23) for MoCA-defined cognitive impairment. Individual Cog-4 items correlated with certain MoCA domains, but the strength of association was modest (r=-.44 orientation, -.37 language, -.19 for inattention, and no significant correlation for executive function, P=.72). CONCLUSIONS: Our data suggest that many stroke survivors with MoCA-defined cognitive problems would not be detected by Cog-4. Subtest correlations suggest that Cog-4 may not be a valid measure of the cognitive domains that it purports to describe. Other brief cognitive screening tests may be better suited to acute stroke.
BACKGROUND: Guidelines recommend cognitive screening for all stroke survivors but do not suggest a preferred tool. Certain elements (orientation, executive function, language, and inattention) of the impairment scale, National Institutes of Health Stroke Scale (NIHSS), have been suggested as a short cognitive screening test-Cog-4. We aimed to describe accuracy and validity of Cog-4 against a more detailed cognitive assessment (Montreal Cognitive Assessment [MoCA]). METHODS: We assessed consecutive acute stroke unit admissions in 2 hospitals over 3 months. Four independent blinded assessors performed NIHSS and MoCA between days 1 and 4 poststroke. We described test properties of Cog-4 for MoCA-defined cognitive impairment using usual thresholds (Cog-4≥1 and MoCA<26 of 30) and described the correlations of individual Cog-4 components with broadly equivalent MoCA domains. RESULTS: We assessed 173 participants; 166 had Cog-4 data and 148 MoCA. MoCA described 84% (n=124) of assessed participants as having cognitive impairment and the Cog-4, 37% (n=62). Cog-4 had a sensitivity of .36 (95% confidence interval [CI]: .28-.45) and a specificity of .96 (95% CI: .80-.99) (positive predictive value: .98, negative predictive value: .23) for MoCA-defined cognitive impairment. Individual Cog-4 items correlated with certain MoCA domains, but the strength of association was modest (r=-.44 orientation, -.37 language, -.19 for inattention, and no significant correlation for executive function, P=.72). CONCLUSIONS: Our data suggest that many stroke survivors with MoCA-defined cognitive problems would not be detected by Cog-4. Subtest correlations suggest that Cog-4 may not be a valid measure of the cognitive domains that it purports to describe. Other brief cognitive screening tests may be better suited to acute stroke.