Longitudinal and cross-sectional validation of the WERCAP screen for assessing psychosis risk and conversion

Abstract

Background: The Washington Early Recognition Center Affectivity and Psychosis (WERCAP) Screen was developed to assess risk for developing psychosis. Its validity has not been investigated in a large population-based study or with longitudinal analyses.

Methods: 825 participants, aged 14-25, were recruited from Kenya. Symptoms were assessed using the WERCAP Screen, as experienced over the prior 3-months (3MO), 12-months (12MO) or lifetime (LIF). ROC curve analysis was used to determine the validity of the WERCAP Screen against the Structured Interview of Psychosis-Risk Syndromes. Longitudinal validity was assessed by comparing baseline p-WERCAP scores in psychotic disorder converters and non-converters, and using ROC curve analysis. Relationship of the p-WERCAP was examined against clinical variables.

Results: ROC curve analyses against SIPS showed an AUC of 0.83 for 3MO, 0.79 for 12MO and 0.65 for LIF psychosis scores. The optimal cut-point on 3MO was a score of >12 (sens: 0.78; spec: 0.77; ppv: 0.41), and >32 for 12MO (sens: 0.71; spec: 0.74; ppv: 0.24). Baseline 3MO scores (but not LIF scores) were higher in converters compared to high-risk non-converters (p = 0.02). 3MO scores against conversion status had an AUC of 0.75, with an optimal cutoff point of >16 (sens: 1.0; spec: 0.53). All p-WERCAP scores significantly correlated with substance use and stress severity. 12 MO scores were most related to cognitive impairment.

Conclusions: The WERCAP Screen is a valid instrument for assessing psychosis severity and conversion risk. It can be used in the community to identify those who may require clinical assessment and care, and for recruitment in psychosis-risk research.

Keywords: Kenya; Psychosis; Risk; Stress screen; Validation; WERCAP.

Fig. 1.. Flowchart depicting participant selection and timeline for the two cohorts. Both cohorts were screened using the WERCAP Screen.

^aFor Cohort 1, ‘lifetime symptoms’ and for Cohort 2, ‘12-month symptoms’ were specified during screening. ^bFor both cohorts, a psychosis score of ≥30 or greater was considered a high score. All high scorers in both cohorts were selected for the study. In Cohort 1, low scorers were selected among those with scores 0–29 with the goal of achieving relatively even representation across the score distribution. In Cohort 2, low scorers were randomly selected among those with scores 0–29.

Fig. 2.. Distribution of p-WERCAP scores across the two youth cohorts.

Figures depict the prevalences of different p-WERCAP score ranges. Cohort 1 participants completed WERCAP screens with 3-month and lifetime symptom timeframes (A). Cohort 2 participants completed WERCAP Screens with 3-month and 12-month symptom timeframes (B).

Fig. 3.. Comparison of p-WERCAP ROC curves by symptom timeframe.

Figures show ROC curves involving p-WERCAP scores against Structured Interview of Psychosis-Risk Syndromes (SIPS)-based clinical high risk (CHR) classification. In (A) ROC curves for 3-month symptom timeframe p-WERCAP scores are compared between Cohort 1 (blue) and Cohort 2 (green) participants. In (B) ROC curves for lifetime symptom timeframe p-WERCAP scores from Cohort 1 (blue) participants are compared to 12-month symptom timeframe p-WERCAP scores from Cohort 2 (green) participants. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4.. Baseline p-WERCAP scores for psychotic disorder converters and non-converters.

The graphs compare baseline p-WERCAP scores in psychosis converters (red; n = 5), high-risk nonconverters (pink; n = 130), and controls (black; n = 142). High-risk status was defined as having CHR status on the SIPS or scores >30 on the lifetime p-WERCAP. Comparison statistics indicate results of Student t-tests. *p < 0.05. ***p < 0.0005. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5.. 3-month p-WERCAP ROC curves against psychosis conversion.

The figure depicts the ROC curve generate using scores from the 3-month symptom timeframe p-WERCAP against psychosis conversion over a 20-month longitudinal study. Psychosis converters (n = 5) and non-converters (n = 272) were ascertained using the SIPS and the Diagnostic Interview Schedule.