Clinical Outcome Assessment Instruments in Schizophrenia: A Scoping Literature Review with a Focus on the Potential of Patient-reported Outcomes

Objective: The complexity inherent in the treatment of schizophrenia results in a multitude of outcome assessments being employed when conducting clinical trials. Subjective outcome assessments and minimal clinically important differences (MCIDs) to evaluate clinical meaningfulness have gained traction; however, the extent of application in evaluation of treatments for schizophrenia is unknown. A scoping review was conducted to assess the availability of published psychometric evaluations, including MCIDs, for clinical outcome assessments used to evaluate treatments for schizophrenia.

Method of research: Key databases (PubMed®, Embase®, APA PsycINFO®, International Society for Pharmacoeconomics and Outcomes Research) were searched for studies on schizophrenia published from 2010 to 2020. Secondary sources (ClinicalTrials.gov, PROLABELS™, FDA.gov) were also reviewed. Clinical outcome assessments were organized by type (patient-reported outcomes [PROs], clinician-reported outcomes [ClinROs], observer-reported outcomes [ObsROs]) and further classified by intended use (generic, mental health, schizophrenia). Reliability and internal consistency were evaluated using Cronbach's α. External validity was evaluated by intraclass correlation coefficient (ICC).

Results: Across 140 studies, 66 clinical outcome assessments were identified. MCIDs were reported for eight of the 66 studies. Of these, two were PROs (generic) and six were ClinROs/ObsROs (three mental health-specific, three schizophrenia-specific). Reliability was good across generic, mental health-specific, and schizophrenia-specific categories, whereas external validity was strong mainly for schizophrenia-specific PROs. Overall, ClinROs/ObsROs that focused on mental health had good reliability and strong external validity.

Conclusion: This review provides a comprehensive overview of the clinical outcome assessments used in schizophrenia research during the past ten years. Results highlight the heterogeneity of existing outcomes and a growing interest in PROs for schizophrenia.