THE SCHEDULE FOR SCHIZOTYPAL PERSONALITIES (SSP) - A DIAGNOSTIC INTERVIEW FOR SCHIZOTYPAL FEATURES

The validity and reproducibility of human psychiatric diagnosis are crucial to psychiatric research. To establish confidence in assigning schizotypal features, 3 paradigms estimating the reliability of a new instrument, the Schedule for Schizotypal Personalities (SSP), were tested. The 1st paradigm considered joint, but independent, evaluations made by 2 raters simultaneously. The 2nd paradigm assessed evaluations on different occasions, with a mean interim time of 5.9 mo. (test-retest procedure). Both reliability paradigms demonstrated high levels of agreement for all of the scaled items. Of the intraclass r = 90% were 0.80 or better for the joint evaluations and 70% were 0.80 or better for the test-retest evaluation. The 3rd paradigm measured the reliability of DSM-III (Diagnostic and Statistical Manual of Mental Disorders-III) schizotypal personality disorder. The kappa value for measuring diagnostic agreement was 0.88. The use of the SSP is recommended as an interview schedule. The implications of the findings for genetic and biological research of schizophrenia spectrum disorders were discussed.