Outcome of individuals “not at risk of psychosis” and prognostic accuracy of the Basel Screening Instrument for Psychosis (BSIP)

Background: We aimed to determine the prognostic accuracy of the Basel Screening Instrument for Psychosis (BSIP) in terms of specificity, sensitivity, positive and negative predictive value by following up individuals that were initially not considered to be at increased risk of psychosis based on the BSIP. Moreover, clinical characteristics of these individuals were examined given the relative lack of such information in the literature. Methods: As part of the “Früherkennung von Psychosen” (FePsy) study, 87 individuals were screened with the BSIP. Of these, 64 were classified at baseline as being in an at-risk mental state (ARMS+) for psychosis using the BSIP and followed up at regular time intervals for at least 2 years to determine a putative transition to psychosis. Twenty-three individuals were classified at baseline as not being in an at-risk mental state (ARMS–) using the BSIP and re-assessed after 4 years. Sensitivity, specificity, positive and negative predictive value of the BSIP were computed. Clinical characteristics of the ARMS– group were analysed descriptively. Results: During the follow-up period, none of the ARMS– individuals, but 21 of ARMS+ had developed psychosis. Sensitivity of the BSIP was 1.0, specificity was 0.35. The majority of ARMS– individuals showed depressive disorders or anxiety disorders and varying levels of functioning. Conclusions: The BSIP has good prognostic accuracy for detecting the prodromal phase of psychosis with an excellent sensitivity and a specificity similar to other risk instruments and the advantage of a relatively short duration. Depressive and anxiety symptoms commonly develop in ARMS– individuals.