Exclusion criteria and generalizability in bipolar disorder treatment trials

Objective

The current paper reviews the English-language research on exclusion criteria in bipolar disorder treatment trials and discusses how study samples compare to the general bipolar patient population.

Methods

& Results: Across 8 identified studies of exclusion criteria and their impact, between 55% and 96% of people with bipolar disorder would be excluded from treatment research. The number of exclusion criteria varies across bipolar disorder treatment research, with one study estimate of a median of 7 criteria used across studies. The criteria that excluded the greatest number of potential participants were comorbid substance use disorder, suicidal risk, and comorbid medical conditions. Both studies that compared treatment responses among participants who met and did not meet exclusion criteria found no statistically significant differences.

Conclusions

Most potential participants are excluded from outcome research, which creates challenges for recruitment and limits generalizability of study findings. Common exclusionary practices lead to unrepresentative samples that limit generalizability and reduce the confidence of clinicians that findings can be translated to front-line practice with bipolar disorder patients.

Generalizability of Clinical Trial Results for Adolescent Major Depressive Disorder

BACKGROUND

Although there have been a number of clinical trials evaluating treatments for adolescents with major depressive disorder (MDD), the generalizability of those trials to samples of depressed adolescents who present for routine clinical care is unknown. Examining the generalizability of clinical trials of pharmacological and psychotherapy interventions for adolescent depression can help administrators and frontline practitioners determine the relevance of these studies for their patients and may also guide eligibility criteria for future clinical trials in this clinical population.

METHODS

Data on nationally representative adolescents were derived from the National Comorbidity Survey: Adolescent Supplement. To assess the generalizability of adolescent clinical trials for MDD, we applied a standard set of eligibility criteria representative of clinical trials to all adolescents in the National Comorbidity Survey: Adolescent Supplement with a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosis of MDD (N = 592).

RESULTS

From the overall MDD sample, 61.9% would have been excluded from a typical pharmacological trial, whereas 42.2% would have been excluded from a psychotherapy trial. Among those who sought treatment (n = 412), the corresponding exclusion rates were 72.7% for a pharmacological trial and 52.2% for a psychotherapy trial. The criterion leading to the largest number of exclusions was "significant risk of suicide" in both pharmacological and psychotherapy trials.

CONCLUSIONS

Pharmacological and, to a lesser extent, psychotherapy clinical trials likely exclude most adolescents with MDD. Careful consideration should be given to balancing eligibility criteria and internal validity with applicability in routine clinical care while ensuring patient safety.

Rethinking vulnerable groups in clinical research

Vulnerable groups are often excluded from clinical research on the basis of scientific, ethical and practical reasons. Although intended to protect vulnerable people and maintain study integrity, exclusion of vulnerable groups from research through use of standard exclusion criteria may not always be necessary and may result in findings that are not generalisable. Achieving a balance between the competing needs to protect vulnerable people and to make progress in our understanding of disorders and their management through research requires a reconsideration of exclusion criteria and consent processes to ensure vulnerable people are appropriately represented in clinical research. Reasons for development of broad exclusion criteria include both concrete barriers and intangible discouraging factors. This paper examines this situation and its consequences, perceived and real barriers to inclusion of vulnerable people in research, and suggests methods for overcoming these barriers and applying thoughtful exclusion criteria.

Implications of Eligibility Criteria on the Generalizability of Alcohol and Drug Treatment Outcome Research: A Study of Real-World Treatment Seekers in Sweden and in Australia

BACKGROUND

Clinical studies of alcohol and drug treatment outcomes frequently apply participant eligibility criteria (EC), which may exclude real-world treatment seekers, impairing the representativeness of studied samples. Some research exists on the impact of EC on alcohol treatment seekers. Little is known about drug treatment and country differences.

OBJECTIVES

We tested and compared the degree to which commonly used EC exclude real-world treatment seekers with problem alcohol and drug use in Sweden and Australia, and compared the impact of EC on outcomes.

METHODS

Two large naturalistic and comparative service user samples were used. Respondents were recruited in Stockholm County (n = 1,865; data collection 2000-2002), and Victoria and Western Australia (n = 796; in 2012-2013). Follow-up interviews were conducted after 1 year. Cross-tabulations, Chi-square (χ²) tests and logistic regressions were used.

RESULTS

Percentages of the samples excluded by individual EC ranged from 5% (lack of education/literacy) to 70% (social instability) among Swedish alcohol cases and from 2% (low alcohol problem severity) to 69% (psychiatric medication) among Australian counterparts; and from 2% (age 60+ years) to 82% (social instability) among Swedish drug cases and from 1% (age 60+ years) to 67% (psychiatric medication) among Australian counterparts. Country differences and differences across substances appeared independent of country effect. Co-morbid psychiatric medication, noncompliance, poly drug use, and low education EC caused positive 1-year outcome bias; whereas female sex and old age introduced negative outcome bias. Conclusions/Importance: Commonly used EC exclude large proportions of treatment seekers. This may impair generalizability of clinical research, and the effects of many EC differ by country and drug type.

Exclusion criteria in treatment research on alcohol, tobacco and illicit drug use disorders: A review and critical analysis

ISSUES

High rates of exclusion in substance use disorder treatment studies reduce the external validity and clinical utility of research findings to an unknown extent. Accordingly, the current review examined commonly used exclusion criteria and their effect on study samples and outcomes.

APPROACH

English-language literature was identified by PubMed searches and review of identified articles' reference lists. Studies were included if they analysed data on: (i) the prevalence and nature of exclusion criteria in the substance use disorder treatment field; and/or (ii) the impact of exclusion criteria on sample representativeness or study results.

KEY FINDINGS

The search yielded 22 studies examining different aspects of exclusion criteria, including 15 empirical examinations of the impact of study exclusion criteria across different substance use disorder treatments on enrolment and outcome results. Aggregating across these 15 studies, we estimated that between 64 and 96% of potential study participants are excluded from substance use disorder treatment studies.

IMPLICATIONS

The widespread exclusion of large proportions of people with substance use disorders limits the external validity of the substance use disorder treatment research literature.

CONCLUSION

Although some eligibility criteria are necessary to protect participant safety and ensure internal validity, researchers conducting studies on substance use disorder treatments should thoughtfully consider the justification for and specific operationalisation of the extensive exclusion criteria they often utilise. [Moberg C, Humphreys K. Exclusion criteria in treatment research on alcohol, tobacco and illicit drug use disorders: A review and critical analysis. Drug Alcohol Rev 2017;36:378-388].