Validity of the schizophrenia diagnosis of the psychopathology instrument for mentally retarded adults (PIMRA): a comparison of schizophrenic patients with and without mental retardation.

The Psychopathology Instrument for Mentally Retarded Adults (PIMRA) was designed to assess psychiatric disorders among mildly and moderately mentally retarded persons. In a psychiatric population without mental retardation (n = 53), the PIMRA schizophrenia scale had an internal consistency coefficient alpha = 0.52. By removing one outlier item this increased to alpha = 0.61. By comparing the PIMRA schizophrenia diagnoses with DSM-III-R diagnoses in the psychiatric population, we found an external reliability corresponding to phi = 0.47 and an unweighted kappa = 0.43. Weighting of the mistakes resulted in a weighted kappa (w) = 0.74. A regression analysis of DSM-III-R diagnosis based on the PIMRA items was conducted. The regression equation was able to identify 75.5% of the DSM-III-R schizophrenic disorders in the psychiatric population. This equation correctly identified 75.5% of the PIMRA schizophrenias in a mentally retarded population. The intermethod reliability was phi = 0.49. We also compared the 38 psychiatric patients with DSM-III-R schizophrenic disorder with the 48 mentally retarded patients with PIMRA schizophrenic disorder. The mentally retarded patients had less delusions and more incoherence and flat affect. They also used less neuroleptic drugs.