Comparison of pervasive developmental disorder and schizophrenia by the Japanese version of the National Adult Reading Test

Objective. In adults, it is sometimes difficult to discriminate between pervasive developmental disorder (PDD) and schizophrenia (SCH) when positive symptoms are not outstanding. We examined whether the Japanese version of the National Adult Reading Test (JART), is a valid scale for evaluating pre-morbid intelligence quotient (IQ) in patients with SCH, and the Wechsler Adult Intelligence Scale-Revised (WAIS-R) are useful for helping to discriminate between PDD and SCH. Methods. Sixteen patients with adult PDD and 16 age-, education- and sex-matched patients with SCH participated in the present study. In addition, two groups were matched for JART and GAF scores. All subjects were scored on the JART and WAIS-R after informed consent on the aim of this study. Examiners who were blind to the diagnoses measured JART and WAIS-R. Results. Significant diagnosis-by-IQ examination interactions were found (F[1,30] = 10.049, P = 0.003). Furthermore, WAIS-R scores of the PDD group were higher than those of the SCH group (P = 0.002) considering two groups were matched for JART. Conclusions. The comparison of IQ in the PDD group and in the SCH group by JART and WAIS-R might be an easy and useful method for helping to discriminate between PDD and SCH.