Prospective identification of individuals at risk of psychosis (“prodromal state”) is necessary for early intervention. This paper gives a comprehensive overview of the different prospective assessment instrument used today and a discussion of their role in the diagnostic process. This paper describes 7 diagnostic instruments and 6 screening instruments. Most of the instruments are based on identification in a help-seeking, symptomatic patient group, referred to the different clinics because of suspicion of prodromal symptoms, but there are also made attempts of screening in a broader symptomatic patient group or in the general population since evidence show that only a portion of the individuals with increased risk seek help for mental problems in the early state. A diagnostic approach based on attenuate positive symptoms gives an annual transition rate varying between 9 % and 54 % in a help-seeking patient group, depending on instrument used and time to follow-up. The most used instruments likelihood ratios are between 2 and 3. The high transition rates in the studies may be partly due enrichment strategies through selectively filtering at-risk individuals out over a range of consecutive referral processes. Today none of the instruments have high enough specificity to be applied to the general population because of high false-positive rate. But screening with an instrument with high sensitivity in a help-seeking patient group, e.g. patients in general practice or clients of counselling services etc., to select individuals for a more detailed risk assessment, may be cost-effective and increase the overall sensitivity.
This paper also gives a discussion whether prodromal state of psychosis should be included as a diagnosis in DSM-V.