Abstracts

The Minnesota Multiphasic Personality Inventory [ndash] 2 (MMPI-2) is an objective, self-report instrument that is used frequently to examine personality and psychopathology in patients with epilepsy. One advantage of this test is that it provides validity indicators useful for identifying biases in responding that could potentially invalidate its results. The goal of this study is to examine the rates of invalid MMPI-2 profiles in a sample of patients undergoing VEEG monitoring for the diagnosis and treatment of epilepsy. MMPI-2 profiles were obtained from 126 patients undergoing continuous inpatient VEEG monitoring. The mean age of the sample was 37.1 years (range, 17 to 74 years). The sex distribution was 74.6% female. Non-epileptic seizures (NES group) were identified in 75 patients. Fifty-one patients had VEEG findings indicating partial (N = 30) or generalized (N = 21) epilepsy (ES group). The groups were matched in terms of age, education, and IQ. The NES group had a higher proportion of females (87% vs. 57%, P [lt] .01). All subjects completed the 567-item version of the MMPI-2 . Analyses were conducted on standard validity indices, including the L, F, and K-scales, as well as the consistency indices, VRIN and TRIN. We also examined two other validity measures, the Fp-scale and the FBS-scale. The former was developed for assessment of rarely endorsed symptoms in populations with high rates of psychopathology. The latter (FBS, Fake-Bad-Scale) is used for measuring reporting bias in injury claimants attempting to exaggerate symptoms while maintaining a socially desirable appearance. Rates of invalid responding, as defined by scores exceeding published cutoffs, were assessed through standard tests of proportions. Invalid MMPI-2 profiles were identified in 43.6% of the total sample. A significantly higher rate of invalid responding was observed in the NES group than in the ES group (53.3% vs. 29.4%, P [lt] .001). Invalid profiles were obtained in only 18.6% of the NES group and 17.6% of the ES group when limited to analysis of conventional validity indices (e.g., L, F, K, VRIN, [amp] TRIN; Chi-Square, NS). None of the 126 subjects participating in this study exhibited an elevation of the Fp-Scale. Elevations of the FBS-Scale were observed in 44.0% of the NES group and in 21.6% of the ES group (P [lt] .001). Over 40% of our sample produced invalid MMPI-2 profiles, which raises concern about the prevalent use of the instrument in this population. Rates of invalid responding in the NES and ES groups were the same when identified through standard validity indices. Higher rates of invalid responding observed with the FBS-Scale indicate that patients with NES are twice as likely to produce exaggerated test profiles than patients diagnosed with partial or generalized epilepsy.