A comparison of MMPI-2 decision rules in the diagnosis of nonepileptic seizures.

The differential diagnosis of epileptic seizures (ES) and psychogenic nonepileptic seizures (PNES) continues to be a common concern in epilepsy treatment centers. The MMPI/MMPI-2 is the most commonly studied psychological measure in the differential diagnosis of ES and PNES. Wilkus, Dodrill, and Thompson (1984) and Derry and McLachlan (1996) both developed decision rules for use with the MMPI and MMPI-2 to assist in this diagnostic discrimination. Both sets of decision rules were evaluated in a sample of ES (n=58), PNES ( n=29) and epilepsy plus PNES (n=19) patients. Validity of the epilepsy diagnosis was established with 24-hr video-EEG monitoring in all cases. The two sets of decision rules applied to the MMPI-2 showed sensitivities of 68% and 48% and specificity values of 55% and 58%. Calculation of positive and negative predictive power for both sets of rules at three different base rates suggests that use of these rules can result in a large number of false positive diagnoses of PNES.