Detection of postoperative cognitive decline after coronary artery bypass graft surgery is affected by the number of neuropsychological tests in the assessment battery.
BACKGROUND
The assessment of postoperative cognitive dysfunction after coronary artery bypass graft surgery is made with the repeated administration of cognitive tests. This classification is vulnerable to error, and it has been suggested that increasing the number of tests in a battery while maintaining constant inclusion criteria for postoperative cognitive dysfunction increases the rate of false positive classification of deterioration. The current study tested this by applying a constant rule for cognitive dysfunction using combinations of two to seven cognitive tests.


METHODS
Two hundred and four coronary artery bypass graft patients (surgical) and 90 healthy nonsurgical controls aged 55 years or older completed a battery of cognitive tests at baseline (preoperative) and 1 week later (postoperative). In both groups, postoperative cognitive dysfunction was classified using all unique combinations of two to seven cognitive tests when performance deteriorated on two or more tests by at least the value of the baseline standard deviation.


RESULTS
The average incidence of cognitive dysfunction progressively increased in both groups as the number of cognitive tests increased from two (surgical: 13.3%; control: 3.1%) to seven tests (surgical: 49.4%; control: 41.1%).


CONCLUSIONS
Increasing the number of tests used to classify postoperative cognitive dysfunction appears to increase the sensitivity to change in the coronary artery bypass graft group. However, accompanying false positive classifications suggest that this improved sensitivity reflected increased error. Future rules for postoperative cognitive dysfunction need to account for this error and include a control group.
Lewis
Matthew S
MS
Centre for Anaesthesia and Cognitive Function, Department of Anaesthesia, St. Vincent's Hospital, Victoria Parade, Melbourne, Australia. matt.lewis2@gmail.com
Maruff
Paul
P
Silbert
Brendan S
BS
Evered
Lis A
LA
Scott
David A
DA
D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D001026:Coronary Artery Bypass; D017558:Elective Surgical Procedures; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D011237:Predictive Value of Tests