Accuracy of the Clock Drawing Test in Screening for Early Post-Stroke Neurocognitive Disorder: The Nor-COAST Study

Abstract

BACKGROUND Post-stroke neurocognitive disorder (NCD), though common, is often overlooked by clinicians. Moreover, although the Montreal Cognitive Assessment (MoCA) has proven to be a valid screening test for NCD, even more time saving tests would be preferred. In our study, we examined the accuracy of the Clock Drawing Test (CDT) in diagnosing patients with post-stroke NCD and the association between the CDT and MoCA. METHODS This study is part of the Norwegian Cognitive Impairment After Stroke study, a multicentre prospective cohort study following patients admitted with acute stroke. At the three-month follow-up, patients were classified with normal cognition, mild NCD or major NCD according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria. Any NCD compromised both mild- and major NCD. The CDT, as part of the MoCA at the three-month assessment, was given scores ranging from 0 to 5. Patients able to complete the CDT and whose cognitive status could be classified were included in analyses. The CDT accuracy for diagnosing post-stroke NCD was examined using receiver operating characteristic (ROC) curves, sensitivity, specificity, positive predictive value, and negative predictive value. The association between the MoCA and CDT was analysed with Spearman’s rho. RESULTS Of 554 participants, 238 (43.0%) were women. Mean (SD) age was 71.5 (11.8) years, while mean (SD) National Institutes of Health Stroke Scale score was 2.6 (3.7). The area under the ROC curve of the CDT for major NCD and any NCD was 0.73 (95% CI, 0.68–0.79) and 0.68 (95% CI, 0.63–0.72), respectively. A CDT cutoff of < 5 yielded 68% sensitivity and 60% specificity for any NCD and 78% sensitivity and 53% specificity for major NCD. Spearman’s correlation coefficient between scores on the MoCA and CDT was 0.50 (95% CI, 0.44–0.57, p < .001). CONCLUSIONS The CDT is not accurate enough to diagnose post-stroke NCD but shows reasonable accuracy in identifying major NCD. Performance on the CDT was associated with performance on MoCA; however, the CDT is inferior to MoCA in identifying post-stroke NCD. TRIAL REGISTRATION ClinicalTrials.gov (NCT0265053)