Rapid cognitive assessment: Accuracy and discriminant validity of Mini-Cog and process-based Clock Drawing Test.

Abstract

Background: The Mini-Cog is a brief cognitive examination comprising a three-item memory recall and a simplified Clock Drawing Test (CDT). There is limited research on the effects of detailed scoring criteria for the Mini-Cog on cognitive screening.

Objective: To assess the diagnostic effectiveness of three Mini-Cog versions and a new process-based CDT test in identifying mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared to cognitively normal controls (NC).

Methods: We prospectively enrolled 950 subjects who underwent standardized neuropsychological assessments and the Mini-Cog test. The CDT was scored using an adapted 10-point scale. The accuracy of three Mini-Cog versions (Mini-Cog1: 3-word delayed recall + 2-point CDT; Mini-Cog2: 3-word immediate recall + 3-word delayed recall + 3-point CDT; Mini-Cog3: 3-word immediate recall + 3-word delayed recall + 10-point CDT) was assessed through the receiver operating characteristic analysis. Sensitivity and specificity were determined for each diagnostic threshold.

Results: The optimal cut-off point for Mini-Cog3 is 12/16 for MCI and 10/16 for AD. Mini-Cog3 demonstrated the highest diagnostic efficacy, with AUCs of 0.82 (95% CI: 0.78-0.85) for MCI and 0.95 (95% CI: 0.94-0.97) for AD, with sensitivity of 85% for both MCI and AD. The CDT's AUCs were 0.77 (95% CI: 0.73-0.81) for MCI, and 0.87 (95% CI: 0.84-0.90) for AD, with sensitivity of 89% for MCI, and 82% for AD.

Conclusions: A more elaborate scoring system, such as Mini-Cog3, may serve as an effective screening method for the rapid and accurate detection of cognitive dysfunction in patients with MCI and AD.