In this study, we examined the preliminary concurrent validity of a brief version of the Prodromal Questionnaire (PQ-B), a self-report screening measure for psychosis risk syndromes. Adolescents and young adults (N = 141) who presented consecutively for clinical assessment to one of two early psychosis research clinics at the University of California, San Francisco and UC Los Angeles completed the PQ-B and the Structured Interview for Prodromal Syndromes (SIPS) at intake. Endorsement of three or more positive symptoms on the PQ-B differentiated between those with prodromal syndrome and psychotic syndrome diagnoses on the SIPS versus those with no SIPS diagnoses with 89% sensitivity, 58% specificity, and a positive Likelihood Ratio of 2.12. A Distress Score measuring the distress or impairment associated with endorsed positive symptoms increased the specificity to 68%, while retaining similar sensitivity of 88%. Agreement was very similar when participants with psychotic syndromes were excluded from the analyses. These results suggest that the PQ-B may be used as an effective, efficient self-report screen for prodromal psychosis syndromes when followed by diagnostic interview, in a two-stage evaluation process in help-seeking populations.
A growing body of research has demonstrated that individuals at “ultra-high-risk” (UHR) for psychosis can be reliably diagnosed using clinical interviews such as the Structured Interview for Prodromal Syndromes (SIPS) (Miller et al., 2003) and the Comprehensive Assessment of At-Risk Mental States (CAARMS) (Yung et al., 2005). Individuals diagnosed with UHR syndromes develop full psychotic disorders at a rate that ranges from 16% to 35% within 2–2.5 years (Cannon et al., 2008, Yung et al., 2007 and Yung et al., 2008). Although these interviews are indispensable in diagnosing prodromal psychosis, clinicians need specialized training to use them and they take several hours of clinicians' and patients' time. Currently, assessment with these instruments is only available in a small number of specialty clinics around the world.
In order to increase efficiency of identifying psychosis risk, we previously developed the Prodromal Questionnaire (PQ), a 92 item-self-report measure intended to be used in a two-stage screening process, followed by prodromal syndrome interviews. In a sample of young people referred to a prodromal psychosis research clinic, the PQ showed moderate concurrent validity with SIPS diagnoses, with 90% sensitivity and 49% specificity (Loewy et al., 2005).
Recently, we modified the PQ to improve efficiency and accuracy. We focused on only positive symptom items, as those are the basis for interview-based diagnoses of symptomatic prodromal syndromes, and we assessed the frequency of each experience and presence of related distress or impairment. In the general population, psychotic-like experiences can be present in up to 20% of adults, often in the absence of a full psychotic disorder (Hanssen et al., 2003). In that study, risk for later psychotic disorder was four to five times greater when individuals were distressed by the psychotic experience compared to those who were not. Undergraduate students endorsed PQ items at very high rates in our own study, but fewer endorsed items as distressing or impairing (Loewy et al., 2007).
Although the ultimate target group for the PQ-B is the general help-seeking population, the first step of measure development is to assess preliminary validity of the PQ-B in a selected help-seeking group that is highly “enriched” for the target diagnoses (McGorry et al., 2003). In the current study, we administered the PQ-B along with the SIPS to all adolescent and young adult patients consecutively presenting to two prodromal psychosis research clinics in California. We hypothesized that: 1) the PQ-B would show good concurrent validity with symptomatic syndromes on the SIPS, similar to the original PQ and 2) assessing frequency of experiences and related distress/impairment would improve specificity of the PQ-B related to these SIPS diagnoses.
