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.
Key Words
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Article info
Publication history
Published online: March 27, 2014
Accepted:
December 29,
2013
Received in revised form:
November 14,
2013
Received:
October 8,
2013
Footnotes
Funding: R.L. is supported by a Chest Heart and Stroke Scotland research grant; this study was supported by a “start up” grant from the British Geriatrics Society (Scotland).
Conflicts of interest: None declared.
Identification
DOI: https://doi.org/10.1016/j.jstrokecerebrovasdis.2013.12.042
Copyright
© 2014 National Stroke Association. Published by Elsevier Inc. All rights reserved.
