title: Cog-4 has limited diagnostic test accuracy and validity for cognitive assessment in stroke survivors.
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.
authors.affiliation: Institute of Cardiovascular and Medical Sciences, School of Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Lees
authors.affiliation: Undergraduate Medical School, School of Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Jane
authors.initials: J
authors.lastname: Lua
authors.affiliation: Undergraduate Medical School, School of Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Emily
authors.initials: E
authors.lastname: Melling
authors.affiliation: Undergraduate Medical School, School of Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Yen
authors.initials: Y
authors.lastname: Miao
authors.affiliation: Undergraduate Medical School, School of Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Jia
authors.initials: J
authors.lastname: Tan
authors.affiliation: Institute of Cardiovascular and Medical Sciences, School of Medicine, University of Glasgow, Glasgow, UK. Electronic address: Terry.quinn@glasgow.ac.uk.
authors.forename: Terence J
authors.initials: TJ
authors.lastname: Quinn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000150:complications* / Q000523:psychology; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D020521:Stroke / Q000150:complications* / Q000523:psychology; D017741:Survivors
keywords: Cog-4; Cognitive impairment; MoCA; scales; screening; sensitivity; specificity; stroke