Quality of Life Measurement Among Persons with Chronic Mental Illness: A Critique of Measures and Methods

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Preface

The primary objective of this work is to provide an informational resource for those who are working in the field of mental health and are considering implementing Quality of Life (QoL) measurement in their clinical practice, evaluation activities or research projects.

The document is intended to cover the basic issues, methods and instruments, an understanding of which is needed to employ QoL measurement in a meaningful way. Issues and methods which are addressed include: definitions of QoL, instrument reliability and validity, the validity of measurement methods, evaluation design, and the role of QoL measurement in mental health planning and policy formulation. Twenty eight (28) instruments are reviewed with respect to the domains of life which they address, the scales and measurement methods they use, their psychometric properties and their use as reported in the recent health literature.

It is hoped that this compendium will serve as an aid to those with a vision towards improving the lives of those they serve.

The authors acknowledge the efforts of Stephanie Wilson, Program Officer and Carol Silcoff, Senior Consultant - Mental Health, Health Canada, in managing this project and publishing the final report.

Executive Summary

This report was commissioned by Health Canada as a result of the identified need by researchers as well as consumers and national professional associations for a critical evaluation of outcomes related to the quality of life of persons with chronic and severe mental disorders.

Quality of life outcome measurement is increasingly recognized as essential, not only among consumers and family members who are seeking an active participation in treatment and other decisions that have an impact on their health and well-being, but also among policy makers who are under mounting pressure to demonstrate value for money in their funding decisions - in this case, to link costs for treatment and related services to mental health status outcomes. At this macro level of analysis, meaningful outcome indicators could contribute to monitoring the effectiveness of mental health reform initiatives under way across Canada.

In order to properly measure quality of life, it is necessary to consider its definition and scope. Certainly, the availability of appropriate and effective mental health services makes an important contribution to clients' life quality; however, mental health care is not the only factor. The complex interplay of internal and external events which impact on the life experience of consumers is elucidated by two theoretical views of the determinants of life quality, namely the functional perspective and the subjective perspective.

Others who take a more psychosocial approach subscribe to the "illness experience" model, i.e., they tend to focus on the more experiential or "subjective" aspects such as distress and disability associated with the illness. Individuals' subjective experience of their quality of life depends on their unique views and values, their experiences over time, and their various social roles, as children, students, family members, employees and patients, among others. Those who take a functional view of quality of life focus on various "objective" aspects of physical and mental functioning. Thus, such things as housing, education and employment play a part in determining quality of life. Measurement of life quality is predicated on one or both of these approaches.

This review examined the Quality of Life (QoL) literature published between January 1991 and January 1996 which addressed quality of life measurement, research methods and related health care policy and planning issues. Of the 386 abstracts reviewed, 137 articles were selected for examination. The objectives of the exercise were to identify quality of life instruments used with a mental health population, or those which utilized some unique measurement methodology, so as to evaluate the psychometric properties of the selected instruments and to conduct a general review of the issues pertaining to quality of life measurement in health care, including policy and planning issues.

Twenty-eight instruments were identified in the process. Approximately two-thirds had been used with a population of persons with chronic and severe mental disorders. These measures were found to cover a range of quality of life dimensions: health status, psychiatric symptomatology, financial situation, living arrangement, family, social/love relationships, leisure/creativity, community productivity, religion and self-esteem/well-being. They varied according to their method of administration (interview, survey), the type of data collected (objective or subjective criteria), the respondent (patient report, professional rating or proxy report) and completion time. The report discusses various considerations brought to bear on the process of instrument selection, with due regard for their properties, as outlined above.

The report also includes a psychometric comparison of instruments. Psychometric properties addressed are reliability, or consistency with which a measurement tool or method gathers information and validity, or the meaningfulness of the instrument and the resultant data. Various aspects of reliability (internal consistency, test-retest and alternate forms) and validity (content and face, construct, concurrent and predictive, and external) are discussed in detail. The twenty-eight instruments selected for this review are then evaluated with respect to their psychometric properties, documented in recent literature.

The authors make the point that, although it is a tempting prospect, they cannot provide a list of the best instruments for use in mental health settings. This is because program (evaluation) staff are in the best position to weigh factors which impact on instrument selection (e.g., type of population(s) they are working with) and on implementation methods, such as determining the quality of life domains of interest (to them and their clients), specifying the need for specific or global measures, balancing cost-effectiveness considerations against the rigour of the investigative method, deciding to use public domain as opposed to purchased tools, and determining the overall purpose of evaluation measurement (e.g., treatment, epidemiological or administrative objectives).

The authors did, however, indicate that they found several instruments that were widely used and validated for a mixed mental health population, a fair indication of their psychometric strength. These instruments include the Health Measurement Questionnaire, Lehman's QoL Interview, QoL Interview Schedule, QoL Inventory and QoL Questionnaire/Interview. Other instruments which show promise with specific populations include the General Health Questionnaire, MOS or SF-36, QoL in Depression Scale, QoL Enjoyment and Satisfaction Questionnaire, Satisfaction with Life Scale, Sickness Impact Profile, and the SmithKline Beecham QoL Scale. Two newly developed scales were also considered to show particular promise, the QoL Index for Mental Health and the QoL Self-Assessment Inventory.

In concluding this portion of the analysis, the authors suggest that there is a need for a comprehensive and standardized comparison of quality of life instruments using several Canadian populations of persons with mental disorders. They also note the need to determine the adequacy of instruments for specific evaluation related tasks, particularly with respect to global versus disease-specific indicators, cost-effectiveness determinations, maintenance of treatment effects and predictive utility of quality of life scales. Training of evaluators, implementation of quality of life measurement in health monitoring systems and system-wide treatment standards are mentioned as elements of strategic planning for future mental health service evaluation and planning in Canada.

In turning the discussion to central issues around quality of life evaluation, the authors explore ways to address complex evaluation issues such as comparisons between outcome indicators gathered with non-standard and disease-specific instruments and comparisons between differing psychiatric populations and programs employing different service delivery models. A range of approaches are discussed, including: measurement of aspects of a patient's health status prior to and following treatment; using subject randomization methods, carefully matched controls, or longitudinal baseline studies; alignment of the dimensions addressed by therapeutic practice and outcome assessment; and calculation of Quality Adjusted Life Years (QALYs) which are gained as a beneficial effect of treatment and then balanced against the costs of service provision.

Other methodological challenges associated with attempts to link outcomes to funding are mentioned, and various ways of addressing the costs of evaluation are explored. This part of the paper concludes with a perspective which transcends the basic question of the effectiveness of services and encompasses the broader issue of how services can promote and support the contribution which mental health "consumers" can make to their communities. Framing the issue in this broader context may have implications when re-balancing the promotion/prevention/treatment equation with client-centered approaches, attempting to improve client self-esteem and community reintegration, and striving for efficiencies in service delivery which maintain or improve the life quality of persons with chronic mental illness.

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