Can A Risk Calculator Predict Conversion to Psychosis?

A risk calculator can predict individualized conversion from prodrome to psychosis, according to a study published online in the American Journal of Psychiatry.

In the majority of patients, onset of psychotic symptoms is preceded by a prodromal phase, in which subtle changes in belief, thought, and perceptions herald eventual full-blown delusions, formal thought disorder, and hallucinations. In high-risk patients with recent onset of these subtler symptoms, an estimated 20% to 30% develop psychosis over a 2-year period.

A team led by Tyrone Cannon, PhD, of Yale University in New Haven, Connecticut created an individualized risk calculator, noting that this approach would yield more accurate information regarding the probability of conversion to psychosis in each individual patient.

The risk calculator was generated using data from 596 clinical high-risk participants (aged 12 to 35 years, mean age 18.5 years) from the second phase of the North American Prodrome Longitudinal Study (NAPLS-2). The calculator took into account demographic, clinical, neurocognitive, and psychosocial predictive variables.

Participants were followed up to the time of conversion to psychosis, or the last contact (up to 2 years). 

The researchers found that 84 patients (16%) converted to psychosis within 2 years, with a mean time of 7.3 months to conversion. The strongest predictors of conversion included prodromal symptom severity, and decline in global social functioning, verbal learning, and memory. Earlier age at baseline and speed of processing were significant only in univariate analysis, the authors stated. They noted that stressful life events, traumas, and family history of schizophrenia were not significant predictors in univariate or multivariate analyses.

The researchers referred to their risk calculator as “well-performing,” noting that the “key advantage of the risk calculator is that it inherently accommodates heterogeneity in profiles of risk factors among clinical high-risk cases” and describing it as “comparable in accuracy to those for cardiovascular disease and cancer.”

The risk calculator is available online. (http://riskcalc.org:3838/napls/) and is intended to assist clinicians.” To address the concern that “untrained individuals” might access the tool and generate high predictive risk scores that could “lead to significant personal distress,” the researchers “built in a decision tree…that requires confirmation of an interview-based SIPS diagnosis of prodromal risk syndrome and confirmation that the ratings and test scores were obtained by a professional.”