by Leslie Citrome, MD, MPH; Marko A. Mychaskiw, BSRPh, MS, PhD; Alma Cortez, BA; Mark Opler, MPH, PhD; Liza Sopina, MPH, PhD; and Sameer Kotak, MS, MBA

Dr. Citrome is with Department of Psychiatry and Behavioral Sciences, New York Medical College in Valhalla, New York. Dr. Mychaskiw and Ms. Cortez are with Global Health Economics and Outcomes Research, Teva Branded Pharmaceutical Products R&D, Inc., in West Chester, Pennsylvania. Dr. Opler is with WCG MedAvante-ProPhase, Inc., in New York City, New York, and The PANSS Institute in Monroe, New York. Dr. Sopina is an Independent Consultant in Odense, Denmark. Mr. Kotak is with Yorker Health in Glen Rock, New Jersey.

Funding: This research was supported by Teva Branded Pharmaceutical Products R&D, Inc.

Disclosures: Dr. Citrome is a consultant for AbbVie/Allergan, Acadia, Adamas, Alkermes, Angelini, Astellas, Avanir, Axsome, BioXcel, Boehringer Ingelheim, Cadent Therapeutics, Cerevel, Clinilabs, COMPASS, Eisai, Enteris BioPharma, HLS Therapeutics, Idorsia, INmune Bio, Impel, Intra-Cellular Therapies, Janssen, Karuna, Lundbeck, Lyndra, Medavante-ProPhase, Marvin, Merck, Mitsubishi-Tanabe Pharma, Neurocrine, Neurelis, Novartis, Noven, Otsuka, Ovid, Praxis, Recordati, Relmada, Reviva, Sage, Sunovion, Supernus, Teva, and University of Arizona, and provides one-off ad hoc consulting for individuals/entities conducting marketing, commercial, or scientific scoping research; is a speaker for AbbVie/Allergan, Acadia, Alkermes, Angelini, Axsome, BioXcel, Eisai, Idorsia, Intra-Cellular Therapies, Janssen, Lundbeck, Neurocrine, Noven, Otsuka, Recordati, Sage, Sunovion, Takeda, Teva, and CME activities organized by medical education companies, such as Medscape, NACCME, NEI, Vindico, and universities and professional organizations/societies; holds stocks (small number of shares of common stock) in Bristol-Myers Squibb, Eli Lilly, Johnson & Johnson, Merck, and Pfizer, purchased over 10 years ago, with stock options in Reviva; receives royalties/publishing income from Taylor & Francis (Editor-in-Chief, Current Medical Research and Opinion, 2022–present), Wiley (Editor-in-Chief, International Journal of Clinical Practice, through the end of 2019), UpToDate (reviewer), Springer Healthcare (book), and Elsevier (Topic Editor, Psychiatry, Clinical Therapeutics). Dr. Mychaskiw and Ms. Cortez are employed by and hold stock in Teva Branded Pharmaceutical Products R&D, Inc. Dr. Opler is employed by WCG Clinical, Inc., and has a leadership role/board member/executive director at The PANSS Institute. Dr. Sopina is consultant for Yorker Health. Mr. Kotak is a consultant for Teva Branded Pharmaceutical Products R&D, Inc.

Innov Clin Neurosci. 2023;20(4–6):14–33.

Abstract

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.

Conclusions: 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.

Keywords: Minimal clinically important differences, patient-reported outcomes, clinician-reported outcomes, psychometric evaluation, quality of life, schizophrenia

The current state of the management of schizophrenia typically involves a combination of pharmacologic and psychosocial interventions;1 however, because of the complexity of the disease, establishing the effectiveness of any treatment is challenging.2 Traditional approaches have focused on measuring psychopathology, including positive symptoms (e.g., delusions, hallucinations, and disorganized speech or behavior) and negative symptoms (e.g., affective flattening, alogia, and avolition), as well as quantifying cognitive impairment.3,4 Other outcomes based on assessment of functioning are also of great interest. However, in contrast to studies on interventions in mood disorders, definitions of response and remission in studies on schizophrenia lack universally accepted or otherwise simple-to-understand definitions; this lack of consensus complicates the process of interpreting the clinical relevance of study results.5,6 Thus, the implementation of standardized, validated clinical outcome assessments can allow researchers and clinicians to make sound inferences regarding the effectiveness of interventions,2 provided that what is meaningful or not can be determined.

Clinical outcome assessments can be broadly divided into clinician- (ClinROs), observer- (ObsROs), or patient-reported outcomes (PROs). There is a rich tradition of utilizing clinician and observer outcomes; however, the self-assessment of patients/subjects can provide different and actionable information. A PRO is “any report of the status of a patient’s health condition that comes directly from the patient, without interpretation of the patient’s response by a clinician or anyone else.”7,8 The potential value of PROs over ClinROs has become more evident relatively recently. The United States (US) Food and Drug Administration (FDA) recommends the use of PROs in pivotal clinical trials.9 Although patients with schizophrenia and their assessments of disease and treatment outcomes may be impacted by anosognosia,10 PROs are still seen as essential to understanding patient preferences for treatments and facilitating comparisons between different therapies.7,8 

The inclusion of PROs in clinical trials is now advised and supported by various guidelines, including some that focus on schizophrenia.11–13 However, selecting a meaningful assessment that reflects the breadth of experiences and symptoms that patients with schizophrenia have and the impact of treatments may be challenging.11–13 A potential solution to this obstacle would be the selection of a PRO with a reported minimal clinically important difference (MCID), which is defined as the minimal amount of change in an outcome assessment that would be important to a patient.14 MCIDs can help guide both clinicians in the assessment of treatment effectiveness and researchers in trial design by providing a rationale for the selection of the most suitable outcome assessment.

In this scoping review, a database and literature search was performed to identify existing outcome assessments used in clinical studies, assess the availability of MCIDs for these assessments used to evaluate patients with schizophrenia, and propose recommendations for furthering MCID research.

Methods

Scoping review design. This scoping review was performed in accordance with the methodology outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA ScR) checklist and the Joanna Briggs Institute guidelines for performing scoping reviews.15,16 The key objective of this review was to identify the existing and relevant clinical outcomes for the assessment of schizophrenia, rather than to assess the quality of studies utilizing these outcomes. 

Literature search strategy. Four key databases (PubMed®, Embase®, APA PsycINFO®, and International Society for Pharmacoeconomics and Outcomes Research [ISPOR; through Value in Health]) were used for this scoping review to assess a large variety of studies of interest. Searches were conducted between April 24, 2020, and April 27, 2020, to reduce the risk of missing newly published studies. EndNote™ X7 was used to import and screen the articles.

Initially, a search utilizing keywords and medical subject headings (MeSH) related to schizophrenia, clinical outcome assessments, and quality of life (QoL) was performed using the PubMed® database. Because Embase® and APA PsycINFO® do not use MeSH terms, keyword-only searches were performed for these databases; where appropriate, wildcard searches were performed to complement keyword-only searches. The ISPOR database does not permit wildcard searches; therefore, a single-word search (“schizophrenia”) was conducted on article titles, abstracts, and keywords. To verify the robustness of this search, an additional search was performed using alternative terms (“schizoaffective”), which yielded results already included in the first search. A summary of the search terms used can be found in Supplementary Table 1.

Studies were included in this analysis if they met the following criteria: published during or after 2010; included patients with existing schizophrenia or schizoaffective disorder diagnosis; and reported on or used a patient-level outcome (patient-reported, observer/clinician-reported) for measuring disease progression, severity, and/or treatment effectiveness in schizophrenia. Any outcomes published only prior to 2010 were not considered for the purposes of this review.

An identified study was excluded from this analysis if the study included patients without schizophrenia or other relevant diagnosis; reported the outcomes of caregivers, partners, or relatives of patients with schizophrenia, but not patient outcomes; reported outcomes in “natural units” (e.g., biologic- or chemical-level, imaging results, life expectancy, hospitalization rate) rather than from an assessment tool or scale; measured the effects of secondary health conditions (e.g., smoking cessation, treatment-related diabetes, or high blood pressure); solely assessed medication adherence; reported utilities (e.g., for calculating quality adjusted life-years) from secondary data; evaluated costs or economic burden/cost minimization; was written as an editorial on clinical outcome assessments in schizophrenia; or not published in English.

Additional secondary sources were reviewed to support the primary literature search. ClinicalTrials.gov was examined for information concerning ongoing or completed schizophrenia-related, interventional, Phase III trials to identify clinical outcome assessments not already identified by the primary literature search. PROLABELS™ (through ePROVIDE™) was searched for the labels of medications approved within the last ten years (2010–2020) by the FDA and European Medicines Agency (EMA) for the treatment of schizophrenia. The identified labels were searched for additional clinical outcome assessments that could be included in this review. The FDA’s website (FDA.gov) was also reviewed for schizophrenia-related submissions to the FDA Clinical Outcome Assessment (COA) Qualification Program. Studies that were known to investigators prior to the literature search were included in this scoping review if they met the inclusion and exclusion criteria.

Data synthesis plan. Clinical outcome assessments that were identified in the scoping review were categorized according to three factors. Each category was divided into various subcategories to appropriately describe the nature of each outcome assessment. The three factors were: 1) who reported the outcome assessment (type), divided into ClinROs, ObsROs, and PROs; 2) focus or intended use of the outcome assessments (focus), divided into generic, mental health, and schizophrenia; and 3) domain of the outcome (domain), divided into QoL/health-related QoL (HRQoL), treatment-related, emotional/psychological wellbeing, symptomatic, cognition, and need for care (Figure 1).

The psychometric properties for all identified clinical outcome assessments were identified to the extent that the literature allowed. The original development and original validation or schizophrenia-specific validation studies were located for each identified outcome assessment, if available. Where possible, the reliability and validity of each outcome assessment, as well as a brief interpretation of each scale or scoring system, were extracted. The performances of outcome assessments were evaluated according to the Consensus‐Based Standards for the Selection of Health Measurement Instruments (COSMIN) guidelines.17 Internal consistency (reliability) was evaluated by the Cronbach’s α method. Reliability was determined to be good if α was 0.8 or greater (+++), acceptable if α ranged from 0.6 to 0.79 (++), and poor or unacceptable if α was less than 0.6 (+/-). From each identified study, the reported intraclass correlation coefficients (ICCs) were assessed for each outcome assessment to determine the external validity. External validity was considered to be strong if ICC was 0.5 or greater (+++), moderate if ICC was 0.25 to 0.49 (++), and weak if ICC was less than 0.25 (+). Furthermore, information on MCIDs was extracted when possible, making note of the treatment modalities.

Results

Literature search. Overall, 2,908 studies were identified by searching the key databases, and 17 studies of interest were identified through known sources prior to the primary literature search (Figure 2). After removing duplicate studies, the titles and abstracts of the remaining 2,329 studies were screened against the inclusion and exclusion criteria. The initial screening yielded 256 studies, which then underwent a full-text review for eligibility. Of those 256 studies, 140 studies were included in this scoping review.11,18–156 Our search of ClinicalTrials.gov identified 294 ongoing or completed randomized controlled trials (RCTs) on schizophrenia with relevant information concerning clinical outcome assessments. A total of 15 EMA-/FDA-approved drugs and the related clinical outcome assessments were extracted from the PROLABELS™ database (Supplementary Table 2). Notably, none of the antipsychotic agents approved between 2010 and 2020 included a mention of PRO endpoints in their respective labels, and all mentioned were ClinROs/ObsROs. Additionally, two outcome assessments (Virtual Reality Functional Capacity Assessment Tool [VRFCAT] and Epidemiological Study of Cognitive Impairment in Schizophrenia [EPICOG]) were identified from schizophrenia-related submissions to the COA Qualification Submissions on the FDA’s website.

Summary of clinical outcome assessments. A total of 66 clinical outcome assessments were identified from the included studies and secondary sources (Table 1). Of these outcome assessments, 26 were ClinROs/ObsROs and 40 were PROs. Among the 26 ClinROs/ObsROs, there were 11 mental health-specific and 15 schizophrenia-specific outcome assessments; no generic ClinROs/ObsROs were reported in the included literature. Among the 40 PROs, there were 11 generic, 15 mental health-specific, and 14 schizophrenia-specific outcome assessments. Of these generic and schizophrenia-specific outcome assessments, select measures specific to cognition (n=5) were added to supplement and strengthen the cognition domain representation.

ClinROs/ObsROs. Nearly half (n=11) of the ClinROs/ObsROs were mental health-specific (Table 2). These 11 outcome assessments were distributed between the QoL/HRQoL (n=3), treatment-related (n=3), symptomatic (n=3), and emotional/psychological wellbeing (n=2) domains. Overall, the mental health-specific outcome assessments identified here had relatively high reliability and strong validity, compared to other outcome assessments.56,57,102,157–168 The remaining 15 ClinROs/ObsROs were schizophrenia-specific (Table 3). Of these 15 outcome assessments, 10 focused on symptoms, while three focused on cognition, and two focused on emotional/psychological wellbeing. The reliability and external validity of the identified schizophrenia-specific assessments varied considerably.23,62,67,76,86,145,146,161,169–175 Certain outcome assessments, such as the Positive and Negative Syndrome Scale (PANSS), had good reliability and strong validity, while newly developed outcome assessments generally demonstrated lower reliability and validity. Reliability and external validity were not available for two outcome assessments.27,36

PROs. A summary of the nine generic PROs is presented in Table 4. All generic PROs were focused on QoL/HRQoL or cognition. Most of the identified generic PROs displayed acceptable reliability, with Cronbach’s α of 0.8 or greater.117,122,176–183 External validity, however, was not particularly strong, whereas variation among the generic outcome assessments was quite high.117,122,176–178,180–183 

Most (n=15) of the identified PROs were mental health-specific (Table 5). Overall, six assessments focused on emotional/psychological wellbeing, four centered on QoL/HRQoL, four assessed treatment-related factors, and one evaluated the need for care. Similar to the generic PROs, the mental health-specific PROs had good reliability, whereas external validity varied.68,107,109,184–193 However, external validity was not available for several mental health-specific PROs.68,107,188,190 Reliability or external validity were not available for two of the treatment-related PROs and the need for care PRO.45,194,195

The remaining PROs were comprised of 14 schizophrenia-specific outcome assessments (Table 6). Among these 14 schizophrenia-specific PROs, more than half (n=8) evaluated QoL/HRQoL and three evaluated cognition. The remaining three schizophrenia-specific PROs were evenly distributed between the treatment-related, emotional/psychological wellbeing, and symptomatic domains. Generally, the QoL/HRQoL PROs were reliable (Cronbach’s α ≥0.8) and had strong validity.35,60,106,125,196–199 The treatment-related schizophrenia-specific PRO had good reliability and acceptable external validity.200 The emotional/psychological wellbeing schizophrenia-specific PRO had good reliability but lacked data on external validity.142 The symptomatic schizophrenia-specific PRO had variable external validity but lacked data on reliability.82

MCIDs. MCIDs were reported for eight of the 66 identified outcome assessments (Table 7).24,50,69,91,138,201–203 Of these eight outcome assessments, six were ClinROs/ObsROs (3 mental health-specific and 3 schizophrenia-specific), while only two were PROs (both generic). One of the outcome assessments, the 36-item Short Form Health Survey (SF-36), reported predetermined MCIDs rather than derived values.69

Discussion

This analysis of schizophrenia-related literature identified 66 individual clinical outcome assessments, which represented patient- and nonpatient-reported outcome assessments, as well as various domains and focuses of outcome assessments for patients with schizophrenia. An advantage of a scoping review over a systematic review, in this context, was the ability to include a broader range of studies and review a larger share of the published literature. This benefit was reflected in the greater number of studies and outcome assessments that we evaluated in this review, as compared to previous efforts over the past decade.25,204,205

The findings of this scoping review highlighted the heterogeneity of existing assessments in terms of scope, focus, and performance. While the reliability of most of the identified ClinROs/ObsROs was good, external validity varied considerably. Weak external validity was noted among newly developed schizophrenia-specific outcome assessments, suggesting a need for further validation through additional research. Overall, mental health- and schizophrenia-specific PROs demonstrated strong psychometric properties (reliability and external validity); these findings were consistent with previous studies.130

The presence of published MCID values for only eight of the 66 identified outcome assessments indicates a substantial gap in knowledge. In particular, none of the schizophrenia-specific PROs had reported MCID values. Additionally, searches performed using the PROLABELS™ database confirmed that PRO endpoints were not mentioned in the labels of any antipsychotic agents approved over the last decade (2010–2020), further highlighting this gap.

While MCIDs are needed to help guide clinical practice and assess treatment effectiveness in research, the development of MCIDs requires substantial investments in research and trial resources. There is no consensus on a universal method for calculating MCIDs for PROs; anchor-based and distributive methods have been the most commonly used for the calculation of MCIDs, with distributive methods being the preferred method in schizophrenia.206,207 By definition, PROs rely on self-report by patients, and the issue of reliability of PROs for MCID calculation has been raised in the literature.207 The main criticism has been that MCIDs based on PROs are unreliable in a population of patients with schizophrenia because of discrepancies between the perceptions of patients and those of other raters (i.e., clinician, observer, or proxy [e.g., family, caregiver]).208 Therefore, the selection of outcome measures should be considered carefully. In this review, criteria for the selection of an outcome measure for MCID evaluation that prioritized multiple aspects of an outcome measure (PROs, mental health- or schizophrenia-specific measures with strong psychometric properties, evidence of use in patients with schizophrenia, and established psychometric properties) were proposed. The application of this criteria to identified outcome measures resulted in a list of recommended outcome assessments for MCID research development. However, the list of suggested outcome measures for MCID evaluation is not exhaustive and only considers the outcome measures that met our recommendation criteria in the strictest sense.

Recommendations for MCID research. Based on the findings of this review, it is recommended that researchers consider the following priorities when selecting an outcome measure for MCID evaluation (Figure 3): type (prioritize PROs because of the lack of reported MCIDs among existing outcome measures), focus (prioritize mental health- or schizophrenia-specific measures based on the strong psychometric properties observed in this scoping review), evidence of use in patients with schizophrenia, and established and acceptable psychometric properties. By applying these criteria, three mental health-specific PROs were identified that should be evaluated for MCIDs: Quality of Life Enjoyment and Satisfaction Questionnaire (QLESQ), Subjective Wellbeing Under Neuroleptic Treatment Scale (SWN), and SWN–Short Version (SWN-K) (Table 8). Furthermore, three schizophrenia-specific PROs with potential for MCID evaluation were identified: Schizophrenia Quality of Life Scale (SQLS), Schizophrenia Quality of Life Questionnaire (SQoL), and SQoL–Short Form (SQoL18; Table 8). As of May 2020, the QLESQ, SWN, and SQLS were being utilized in ongoing Phase III trials indexed on ClinicalTrials.gov.209–229

Limitations. The literature search was limited to studies published during or after 2010 and written in English. The review may have missed relevant outcome assessments used in earlier studies or published in other languages. However, if these missed outcomes were not used in the last decade or were not published in the de facto language of most regulatory agencies and medical research, the impact of their exclusion from our review can be considered minimal. In addition, some outcome assessments lacked reliability and/or validity, which makes comparisons with other assessments difficult. Please note that the categories of mental health- and schizophrenia-specific can appear arbitrary for those measures that can be employed transdiagnostically. Lastly, the strength of the reliability and validity of outcome assessments were only determined with Cronbach’s α method and ICC, respectively, which may have limited the breadth of this review.

Conclusion

This scoping review provided a comprehensive overview of the clinical outcome assessments utilized during the past ten years in the field of schizophrenia and related disorders. The 66 identified outcome assessments were found to be of varying focus, scope, and validity. A large portion of these outcome assessments were patient-reported, indicating the importance of a growing implementation of PROs in the field of schizophrenia. However, none of the schizophrenia-specific PROs had estimated MCIDs, suggesting significant gaps in knowledge and opportunities for future research. Mental health- and schizophrenia-specific PROs overall demonstrated strong psychometric properties (reliability and external validity), and mental health-specific ClinROs/ObsROs generally had good reliability. Additional research is warranted to interpret individual and group level changes in the most sensitive disease-specific PROs.

Acknowledgments

Medical writing and editorial support for the development of this manuscript, under the direction of the authors, was provided by Adel Chowdhury, PharmD; Mark Skopin, PhD, CMPP; Jennifer C. Jaworski, MS, BCMAS, CMPP; and Frederique H. Evans, MBS, all of whom are with Ashfield MedComms, an Inizio company. Medical writing and editorial support were funded by Teva Branded Pharmaceutical Products R&D, Inc.

Author Contributions

All authors contributed to the conceptual design and writing of the manuscript. All authors have approved the final manuscript.

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