Use of normative databases and statistical methods in demonstrating clinical utility of QEEG: importance and cautions.

The clinical utility of the EEG, especially in psychiatric, learning and cognitive disorders, has been greatly enhanced by the use of quantitative analysis (QEEG) and comparisons to a normative database. Of primary importance in the use of such a reference database are the following considerations and cautions: adequate sampling across a broad age range; consideration of inclusion/exclusion criteria; adequate sample of artifact-free data to demonstrate reliability and replicability of norms; demonstration of specificity and sensitivity. A normative database meeting these criteria allows the multivariate description of patterns of QEEG abnormalities in patients as compared to age appropriate normative values, and the exploration of neurophysiological heterogeneity within populations. Demonstrations of the clinical significance of this approach exist in the scientific literature and demonstrate that QEEG provides high sensitivity and specificity to abnormalities in brain function seen in psychiatric populations.