Cog-4 has limited diagnostic test accuracy and validity for cognitive assessment in stroke survivors (original) (raw)

Lees, Rosalind, Lua, Jane, Melling, Emily, Miao, Yen, Tan, Jia and Quinn, Terence J. ORCID: https://orcid.org/0000-0003-1401-0181(2014) Cog-4 has limited diagnostic test accuracy and validity for cognitive assessment in stroke survivors.Journal of Stroke and Cerebrovascular Diseases, 23(6), pp. 1604-1610. (doi: 10.1016/j.jstrokecerebrovasdis.2013.12.042)

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Publisher's URL: http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2013.12.042

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.

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