Application of functional near infrared spectroscopy as supplementary examination for diagnosis of clinical stages of psychosis spectrum.

Aim: Research efforts aiming at neuroimaging-aided differential diagnosis for psychiatric disorders have been progressing rapidly. A previous multisite study has developed a supplementary diagnostic system using functional near-infrared spectroscopy (fNIRS) that can be easily applied to clinical settings. However, few neuroimaging biomarkers have been developed for the psychosis spectrum with various clinical stages.

Methods: We employed the fNIRS as a clinical examination device for 143 participants, comprising 47 ultra-high risk for psychosis (UHR) individuals, 30 patients with first-episode psychosis (FEP), 34 patients with chronic schizophrenia (ChSZ), and 33 healthy controls, who were independent of the previous study. A 12-month follow-up measurement was also carried out on 34 UHR individuals (72%), 21 patients with FEP (70%), and 33 controls. The fNIRS algorithm variables used for classification were the intensity and timing of prefrontal activation following the start of the cognitive task as used in the previous multisite study.

Results: The discrimination rate by timing of activation was modest but it became acceptable after adjusting confounding factors. Discrimination by intensity of activation was not improved by similar adjustment. A total of 63.8%, 86.7%, and 81.3% patients were classified as UHR, FEP, and ChSZ, respectively; and 85.1%, 86.7%, and 71.9% of patients in these groups, respectively, were classified as being on the psychosis spectrum. In the follow-up measurement, 88.2% of individuals with UHR and 95.0% of patients with FEP were successfully classified into the psychosis spectrum group.

Conclusion: The fNIRS for supplementary clinical examination could be validly applied to differentiating people with the psychosis spectrum in various clinical stages. The fNIRS is a candidate biological marker for aiding diagnosis of psychosis spectrum in routine clinical settings.