Cut-Off Values For EEG Frequency in Differentiation of Alzheimer, Non-Alzheimer Dementia and Healthy Subjects:An Application of 3D-ROC Surface Method

Objectives: To write a new macro programme for theuse of the non-parametric 3-D Receiver OperatingCharacteristic (ROC) surface method in the discrimi-nation of three or more groups, to study the useful-ness of electroencephalography (EEG) frequencyin the diagnosis of Alzheimer type dementia (AD),non-Alzheimer type dementia (NAD) and healthysubjects, and to determine cut-off values of EEGfrequency. Patients and Methods: The mean EEG frequen-cies in the left fontal region EEG records of subjectsin the present study were calculated and the ROCsurface method was used in discrimination of the groups. Results: The volume under the ROC surface was calculated as 0.464±0.150. Accuracy of the mean frequency in differentiation of groups was statisticallysignificant (p=0.024). 8 Hz was found to be convenientfor differentiation of AD from NAD patients and 10Hz for the differentiation of NAD patients and healthysubjects. The sensitivity was 87.5% for Alzheimer’s dementia diagnosis and total accuracy was 65% usingthis cut-off pair. Conclusion: We suggest that the mean EEG frequency may be used only as a pre-diagnostic tool for the differ-ential diagnosis of these groups.