The clock drawing test is a poor screening tool for postoperative delirium and cognitive dysfunction after aortic repair

Background

The Clock Drawing Test (CDT) is a screening tool for dementia that tests a variety of cognitive domains. The CDT takes a maximum of two minutes to complete and might be helpful in identifying postoperative cognitive disorders at the bedside. The objective of this study was to evaluate the accuracy of the CDT in a population at high risk for postoperative cognitive disorders

Methods

In this prospective observational cohort study, patients were recruited who were ≥ 60 yr of age and scheduled for elective open repair of the abdominal aorta. Delirium was assessed using the Confusion Assessment Method (CAM) on postoperative days (POD) 2 and 4 and at discharge. Cognitive function was assessed with neuropsychometric tests before surgery and at discharge. Postoperative cognitive dysfunction (POCD) was determined using the Reliable Change Index. Clock Drawing Tests were administered at all time points. Agreement between the CDT and test for delirium or POCD was assessed with Cohen’s Kappa statistic.

Results

Delirium was noted in 30 of 83 patients (36%; 95% confidence interval CI] 26 to 46%) during their hospital stay, while POCD was noted in 48 of 78 patients (60%; 95% CI 51 to 72%) at discharge. Agreement between the CDT and CAM was poor at three intervals (Kappa 0.06 to 0.29), as was POCD at discharge (Kappa 0.46). Sensitivity of the CDT was <0.71 for both delirium and POCD at all intervals. False positives and negatives were common.

Conclusion

Agreement between CDT and tests for delirium and POCD was poor; sensitivity was inadequate for a screening test. (ClinicalTrials.gov number, NCT00911677).