Study participants were 141 individuals age 12-35 who presented consecutively for evaluation at one of two prodromal psychosis research clinics: the Prodrome Assessment, Research and Treatment program at the University of California, San Francisco (UCSF) (N=47) and the Staglin Music Festival Center for Assessment and Prevention of Prodromal States at the University of California, Los Angeles (UCLA) (N=94). Subjects were referred from community clinicians, schools, family members, and self-referred from seeing information about the programs on the internet. Participants at the two sites did not significantly differ from each other on any demographic, psychosocial functioning or diagnostic grouping variables (see .)
Demographic and clinical characteristics of the samples.
A sample of age-matched healthy control participants (HCs) at both sites were recruited for comparison to the patient group through advertisements placed on websites and at local schools. HCs (N=46) were not significantly different from the patient group on age, ethnicity or socioeconomic status, as measured by years of parental education, but had a higher proportion of females than the patient group (p=.045). The control subjects at UCLA were assigned GAF scores, which were significantly higher than those of the patient group, as expected (p<.0001). Details of demographic characteristics are presented in .
The SIPS is semi-structured interview designed to be administered by trained clinicians (Miller, et al, 2003
). The interview includes a biopsychosocial history and ratings along four major symptom dimensions on the Scale of Prodromal Symptoms (SOPS): positive, negative, disorganized and general/affective symptoms. The SIPS/SOPS diagnoses three types of prodromal syndromes, listed in order of typical sample prevalence: 1) Attenuated Positive Symptom Prodromal Syndrome (APS): Attenuated positive psychotic symptoms present at least once per week, started or worsened in that past year (unusual thought content/delusional ideas, suspiciousness/persecutory ideas, grandiosity, perceptual abnormalities/distortions, and conceptual disorganization; 2) Brief Intermittent Psychosis Prodromal Syndrome (BIPS): Brief and intermittent fully psychotic symptoms that have started recently; 3) Genetic Risk and Deterioration Prodromal Syndrome (GRDS): Either a family history of a psychotic disorder in any first-degree relative and decline of at least 30% in the past 12 months on the GAF scale, or, meets criteria for schizotypal personality disorder and has had a decline of 30% on the GAF in the past year.
After SIPS assessment, 44% of subjects were diagnosed with a UHR syndrome, 42% were diagnosed as being fully psychotic, and 13% received no psychotic-spectrum diagnosis. Among UHR subjects, 39 (95%) met APS criteria and two (5%) met BIPS criteria. One GRDS subject was excluded from analyses, as the PQ-B is intended to capture symptomatic at-risk syndromes.
2.2b. Prodromal Questionnaire-Brief Version (PQ-B)
The PQ-B was developed from the original 92-item Prodromal Questionnaire. First, we retained only positive symptom items, as these constitute the basis for symptomatic UHR diagnoses (APS & BIPS). Second, we analyzed the original clinic-referred UCLA sample and selected the positive symptom items with the greatest agreement with SIPS diagnoses. Third, we removed items endorsed by a large proportion of a general undergraduate university sample, as these items were assumed to be easily misunderstood and overendorsed (Loewy, et al, 2007
). This resulted in 18 positive symptom items, two of which were slightly re-worded for clarity. We added five more positive symptom items to assess suspiciousness (2 items), grandiosity (2 items) and disorganized communication (1 item), which were under-represented on the PQ-B relative to items inquiring about unusual thinking and perceptual disturbances. Finally, we added one item on social functioning and one item on academic/occupational functioning. Following each individual item, we included two Likert scale follow-up questions that had been used previously in the undergraduate sample, inquiring about frequency and related distress or impairment. See Appendix A
for a copy of the PQ-B and Appendix B
for details on scoring.
Participants or their parents (for subjects age 12-17) completed a brief phone screen prior to being scheduled for a clinic intake in order to exclude cases of well-established psychosis, mental retardation, substance dependence, and neurological disorders such as temporal lobe epilepsy. Upon arrival at the clinic, participants provided informed consent or assent with parental consent for the study, then completed the PQ-B, followed by the SIPS. Whenever possible, collateral information was obtained by interviewing parents, significant others and relevant clinicians.
A sample of age-matched healthy control participants (HCs) at both sites completed the PQ-B and the SCID to rule out the presence of current Axis I diagnoses. Healthy control subjects at UCLA (N=26) also completed the SIPS.
Clinical interviewers at both sites were MA, PhD or MD- level clinicians who underwent a standard training procedure. Inter-rater reliability was excellent at both sites; ICCs for UCSF staff were 0.94 for SIPS diagnoses and 0.70 to 0.97 for SOPS ratings. All ICCs were above 0.80 at UCLA. Participant diagnoses were discussed in regular reliability rounds to limit rater drift. All study procedures were approved by the human subjects review committees at UCSF and UCLA.
2.4. Statistical Analyses
Subjects with more than 6 items left unanswered on the PQ-B were excluded from the analyses (N=6; 4%). Next, remaining missing data were coded as no (0), based on informal questioning of patients across several studies of the PQ, which suggested that blank items nearly always indicated that participants had not experienced that symptom. Missing data for frequency and distress were also coded as 0, in accordance with how the measure would be used in actual practice. Distributions of PQ-B and SIPS scores were examined for violations of normality assumptions. All scores were skewed towards 0, as expected, and therefore non-parametric statistics were calculated as necessary.
Agreement between PQ-B scores and SIPS diagnoses was used to assess concurrent validity by generating receiver operating characteristic (ROC) curves and calculating areas under the curve (AUCs). Values for sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratios were computed. Correlation analyses were performed between PQ-B scores and SOPS positive symptom scores using Spearman’s correlation coefficient. Cronbach’s coefficient alpha was used to examine internal consistency of the PQ-B. The Kruskal-Wallis test is a non-parametric rank test that was used to compare PQ-B scores across the three SIPS diagnostic groups (no SIPS diagnosis, prodromal syndrome, psychotic syndrome). When significant differences were detected across groups, post-hoc Mann-Whitney U tests then examined paired group contrasts.