Study data published in Schizophrenia Research support the efficacy of the Community Assessment of Psychic Experiences-Positive 15-items Scale (CAPE-P15) for detecting patients at high risk for developing psychosis.
Clare Knight and colleagues at the University of Cambridge in the United Kingdom assessed the discriminatory capacity of CAPE-P15 for psychosis risk among patients with common mental disorders. They performed an analysis of patients who were referred to the Improving Access to Psychological Therapies (IAPT) program at 1 of 3 participating mental health facilities in England.
IAPT-administered CAPE-P15 data were abstracted from 1131 patients with common mental disorders (mean age, 39.7±14.9 years; 65.8% women) between February and August 2018. The CAPE-P15 comprises 2 subscales: frequency of symptoms associated with psychotic experiences and distress associated with psychotic experiences. CAPE-15 reliability was estimated using the McDonald’s hierarchical coefficient. Mean-squares and chi-square values were calculated to evaluate CAPE-P15 subscale items fit to the Rating Scale Model.
The majority (73.5%) of participants scored below the CAPE-P15 threshold score (1.47) for having an ultra-high risk (UHR) for psychosis. Overall, CAPE-15 reliability was high, with cutoff values of 1.30 and 1.29 for the frequency and distress subscales, respectively. Sensitivity was 97.5% for each of these threshold values (CAPE-P15 detected 97.5% of patients with psychotic experiences).
Chi-square values were only statistically significant in both subscales for item 6: “In the past three months, have you felt as if electrical devices such as computers can influence the way you think?” However, CAPE-P15 mean squares were within acceptable limits (0.6-1.4) for the remaining items of both subscales. Per the Rating Scale Model, the lowest CAPE-P15 scores which may be used to indicate UHR for psychosis were 1.20 and 1.07 for the frequency and distress subscales, respectively.
Using these data, the investigators recommended revising the CAPE-P15 cutoff thresholds to 1.30 and 1.29 (or 1.20 and 1.09) for the frequency and distress subscales, respectively. These cutoff values have high sensitivity for psychotic experiences.
As a limitation, investigators noted that increased sensitivity comes at the cost of specificity; lower specificity correlates with increased numbers of false positives. As such, any threshold value revision should be done carefully, with an intent to improve patient outcomes and enhance recovery rates.
Knight C, Stochl J, Soneson E, Russo DA, Jones PB, Perez J. Revisiting CAPE-P15 cut-off values to increase sensitivity for detecting psychotic experiences in primary care [published online December 5, 2019]. Schizophr Res. doi:10.1016/j.schres.2019.11.051