Validation of a Rational Malingering Test Using Evoked Potentials

Malingering is easy to define, difficult to detect, and very costly for any health care system. The structured interview of reported symptoms (SIRS) was constructed using rational strategies to detect malingering in patients endorsing psychotic symptoms. This study validated the SIRS using evoked potentials. Nineteen patients meeting DSM-IV criteria for schizophrenia and 15 healthy controls completed an oddball and paired click protocol. Severity of psychotic symptoms was documented using the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. The patient group was divided by probability of malingering according to the SIRS. Patients with a high probability of malingering had significantly greater P3 amplitude (P = 0.006, t-test) and more P50 suppression (P = 0.044, t-test) than patients with a low probability of malingering. No significant difference in P3 amplitude or P50 suppression was found between the patients with a high probability of malingering and the healthy controls. This study provides empirical support for the validity of the SIRS with evidence that is independent of patient report.