Predictive utility of the Minnesota Multiphasic Personality Inventory-2-RF (MMPI-2-RF) in differentiating psychogenic nonepileptic seizures and epileptic seizures in male veterans

Objective: While psychogenic nonepileptic seizures (PNES) and epileptic seizures (ES) often present similarly, they are etiologically distinct, and correct diagnosis is essential for ensuring appropriate treatment and improving outcomes. The Minnesota Multiphasic Personality Inventory-2-RF (MMPI-2-RF) may assist in differential diagnosis, but prior investigations have been limited by disproportionately female samples, inconsistent accounting for profile invalidity, and limited intra-scale variability from dichotomizing variables. The current investigation addressed these gaps by assessing diagnostic utility of the MMPI-2-RF in differentiating PNES and ES in a male sample of veterans while conservatively accounting for profile invalidity and using a statistical approach that allows for consideration of continuous independent variables to better appreciate intra-scale variance. Method: One hundred and forty-four veterans completed the MMPI-2-RF and were diagnosed with PNES (57.6%) or ES (42.4%) by a board-certified neurologist following continuous video-EEG monitoring. Participants with validity scores falling in the definitely or likely invalid ranges were excluded to ensure construct validity among clinical/substantive scales. Independent samples t-tests assessed differences in MMPI-2-RF variables by diagnostic groups. Hierarchical stepwise logistical regressions assessed predictive utility of MMPI-2-RF indices. A clinical calculator was derived from regression findings to help with diagnostic prediction. Results: Males with PNES endorsed significantly higher scores on F-r, FBS-r, RBS, RC1, RC7, HPC, and NUC (medium to large effect sizes). The regression block that contained validity, restructured clinical (RC1), and substantive scales (GIC, SUI) had a hit rate of 75.69%, which was an improvement from the baseline model hit rate of 57.64%. Higher endorsement on RC1 and lower reporting on GIC significantly predicted PNES diagnosis for males. Conclusions: Minnesota Multiphasic Personality Inventory-2-RF improved diagnostic accuracy of PNES versus ES among male veterans, and RC1 (somatic complaints) emerged as a significant predictor for males with PNES, in line with hypotheses. Several clinical/substantive scales assisted with differential diagnosis after careful accounting for profile validity. Future studies can validate findings among males outside of veteran samples.