The Psychometric Properties of Four Quality of Life Instruments Used in Cardiovascular Populations

Quality of life (QOL) is a complex concept that has become a prominent concern to practitioners caring for those with cardiovascular disease. There are several reasons for the growing emphasis of QOL measures in clinical practice. Prior to World War II, the goal of healthcare generally was palliative in nature. With the explosion of biotechnology and the advent of critical care units, the primary goal of treatment became survival and prolongation of life. 1 Research and clinical practice were aimed at preserving life at all costs and these goals were largely successful. However, technological advances and the resultant high cost of healthcare have led society to reassess the value of the quantity of life and embrace the value of quality of life. As Edlund and Tancredi 2 noted, a patient can be biologically “alive” while at the same time being socially “dead.” Contemporary goals of treatment have expanded to include reducing the severity of symptoms, improving functional status, and improving general QOL. 3 As the population ages and healthcare evolves from an emphasis on acute care to an emphasis on chronic care, the assessment of QOL will become even more important. The purpose of this article is to examine the psychometric properties of 4 QOL instruments used in studies of patients with cardiovascular disease. REVIEW OF RELEVANT LITERATURE There is general agreement that QOL is a multidimensional concept but little agreement as to what items are subsumed in the concept. 4 This is not surprising, as values are socially defined by people living in a dynamic world. Five broad conceptualizations of QOL have been identified in a review of cardiovascular research. The concepts include social usefulness, happiness/affect, satisfaction, achievement of personal goals, and normal life. 5 The variety of definitions used by researchers has made comparisons between populations and between instruments problematic. However, lack of a uniform and explicit definition does not preclude researchers from gathering valid and useful QOL data. It merely serves as a reminder that the concept is implicit, subject to interpretation, and very subjective. 6 Several authors have provided conceptual frameworks for the assessment of QOL. These models have identified several distinct domains, which in sum represent QOL. A model proposed by Ferrans 7 includes health and functioning, psychological/spiritual, social and economic, and family domains (see Table 1). Ferrell et al 8 created a model that includes the dimensions of physical well-being and symptoms, psychological well-being, social well-being, and spiritual well-being (Table 2). These models are quite similar and provide mutual validation as they were developed simultaneously and independently. 7Table 1: FERRANS 7 CONCEPTUAL MODEL FOR QUALITY OF LIFETable 2: FERRELL et al 8 CONCEPTUAL MODEL FOR QUALITY OF LIFEFinally, Wenger et al 9 presented a conceptual framework for the measurement of QOL in clinical trials of cardiovascular therapies. The model includes the domains of functional capacity (including social and emotional), perceptions, and symptoms (Table 3). Health status, economic status, emotional capacity, and life satisfaction are assessed demonstrating that this model also approximates the models created by Ferrans 7 and Ferrell et al. 8 Even though the model by Wenger et al 9 was designed for use in cardiovascular patients, it could be applied to other populations with chronic illness or in trials of therapeutic interventions. The assessment of QOL is further complicated by the following questions: Why explore it? Who should evaluate it? How can it be measured?Table 3: WENGER et al 9 CONCEPTUAL MODEL FOR QUALITY OF LIFE IN CARDIOVASCULAR THERAPIESThe Value of Quality of Life Assessments There are numerous benefits to exploring QOL. According to Stewart, 10 QOL research has descriptive, comparative, predictive, and theoretical benefits. Measures of QOL can provide valuable descriptors of the experiences of a specific population of patients, such as those with cardiovascular (CV) disease. These measures may be used to compare different groups or subgroups including patients with angina, myocardial infarction (MI), congestive heart failure, cardiac interventions, or bypass surgery. Quality of life research may help predict the course of disease, the process of recovery, the usefulness of therapeutic interventions, or the need for specific services. Finally, research into QOL is likely to contribute to the development of new theories of illness, illness behavior, and responses to treatment. Who Should Evaluate Quality of Life? The determination of QOL requires a value judgment. Intuitively, the individual most suited to critiquing a person’s QOL is that individual. Hunt 11 observed that though it is desirable to base QOL assessments on the patient’s views, this often is not reflected in the content of the instruments. In certain instances, the evaluation of QOL may be made by a proxy such as the patient’s physician, nurse, or significant others. However, discrepancies have often surfaced between patient and caregiver’s judgments. 12 There are times when the use of proxy measures serves a useful purpose. The determination of public health policy or the allocation of limited resources are examples. A situation in which the patient is unable or unwilling to participate in an evaluation of their QOL is another example. However, the evaluation of QOL of an individual is subjective in nature, dependent on the individual’s values, and is best evaluated by the patient. 13 Measurement Issues The choice of domains to include, the utilization of generic or disease-specific tools, the use of subjective or objective measures, and repeated measures all are salient issues in the measurement of QOL in patients with CV disease. Support for the reliability, validity, and sensitivity of the tool is a prerequisite for choosing the most suitable QOL instrument for the population under study. This type of evidence gives some assurance that the are that the instrument measures what it is to and is to in QOL. 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