Factor-structure of the Italian version of the Scale Of Prodromal Symptoms (SOPS): a comparison with the English version

Aims. The 19-item 'Scale Of Prodromal Symptoms' (SOPS) and its semi-structured interview, the Structured Interview for Prodromal Symptoms (SIPS), have been developed to assess prodromes of psychosis. We assessed psychometric properties of the Italian version of the instrument. Methods. We collected socio-demographic and clinical data of 128 people seeking first-time psychiatric help in a large Roman area, either as outpatients at community facilities or as inpatients in psychiatric wards of two general hospitals. Participants were administered the Italian version of the SOPS and the 24-item Brief Psychiatric Rating Scale (BPRS). Data were analysed through Pearson's correlation and factorial analysis. Results. The English and Italian SOPS versions showed similar psychometric properties and factorial structure. The best-fit model was trifactorial, explaining 90% of total variance, and roughly corresponding to the positive, negative, and general dimensions, with disorganisation spreading over the other dimensions. Compared with the BPRS, the Italian version of the SOPS showed construct validity and convergent validity. Conclusions. The factor-structure of the Italian version of the SOPS is similar to those of the English and Spanish versions, in that the factors emerged are the same (positive, negative, and general symptoms). The scale could be used to assess at-risk people in early intervention services.