INTRODUCTION — Although difficult to define, quality of life has an inherent meaning to most people. It is comprised of broad concepts that affect global life satisfaction, including good health, adequate housing, employment, personal and family safety, interpersonal relationships, education, and leisure pursuits. For matters related to health care, quality of life has been applied specifically to those life concerns that are most affected by health or illness, hence the term "health-related quality of life" (HRQL) [1].
The concept of HRQL emerged from the broader concept of general quality of life, and is, by definition, more focused on aspects of life quality that are influenced by or can influence one's health status directly. These aspects can include symptoms of disease and treatment side effects, treatment satisfaction, physical functioning and wellbeing, social functioning and life satisfaction, and mental health, including emotional wellbeing and cognitive functioning. HRQL does not typically include aspects of life that are often associated with the broader concept of quality of life, such as income, financial resources, nutrition, and environmental conditions such as air quality, climate, political and personal freedoms, and public safety (crime). Some research has begun to look at some of these broader quality of life domains and their relationship with HRQL. Often referred to as the social determinants of health, these concepts outside of the definition of HRQL are outside the scope of this document.
Specific measures to evaluate the outcome of a serious illness or its treatment include quantity and quality of life, as well as economic cost to the patient (ie, the financial burden of care). Although length of survival has historically been considered the most important among these, the impact of illness on quality of life has received increasing recognition. Since the 1980s, improvement in HRQL has been one of two potential benefits that are considered by the US Food and Drug Administration (FDA) as a basis for full approval of new anticancer drugs [2]. In 2009, the FDA released specific guidance for the development and validation of quality of life measures (also known as patient-reported outcome measures [PROMs]) that could be suitable for regulatory purposes [3]. Further developed by FDA authors in 2016, the recommended quality-of-life components for drug labeling purposes include disease-related symptoms, physical function, and patient-reported adverse events [4]. An ontology for patient-reported outcomes has been published [5].
Historically, HRQL has been a fundamental concern of oncologic practice since 1949, when Karnofsky and Burchenal developed a clinical scale to quantify the functional performance of cancer patients (table 1) [6,7]. Increasing interest in the systematic assessment of HRQL in cancer patients using standardized, self-administered measures has emerged over the past three decades [8] and has become an important focus of benefit for newer therapies [9-14], as well as a basis for documenting the quality of cancer care [15].
HRQL is a particularly important issue for patients who are in the advanced stages of a serious life threatening illness. Palliative care is an interdisciplinary medical specialty that focuses on preventing and relieving suffering and on supporting the best possible quality of life for patients and their families facing serious illness. (See "Benefits, services, and models of subspecialty palliative care".)
Here we will discuss assessment of HRQL in patients with serious life-threatening medical illness, emphasizing malignant disease and palliative care patients. Issues specific to HRQL in patients with head and neck cancer and those undergoing hematopoietic cell transplantation are discussed elsewhere. (See "Health-related quality of life in head and neck cancer" and "Survival, quality of life, and late complications after hematopoietic cell transplantation in adults", section on 'Quality of life'.)
DEFINING HRQL — HRQL can be formally defined as "the extent to which one's usual or expected physical, emotional, and social wellbeing are affected by a medical condition or its treatment" [16]. This definition incorporates the two widely accepted aspects of quality of life: subjectivity and multidimensionality [17].
HRQL represents a subjective appraisal of the impact of illness or its treatment; individual patients with the same objective health status can report dissimilar HRQL due to unique differences in expectations and coping abilities [18]. As a result, HRQL must be measured from the individual's viewpoint rather than that of outside observers (ie, caregivers or health care professionals) whenever possible. The importance of obtaining HRQL reports from patients, themselves, is highlighted by a substantial literature documenting disparate estimates of symptoms and HRQL between patients and their physicians [19].
Multidimensionality is the other important component of HRQL. The multidimensionality of HRQL is reflected in the work of the Patient-Reported Outcomes Measurement Information System (PROMIS), a National Institutes of Health (NIH)-funded national effort that has produced a comprehensive, conceptual framework of self-reported health for adults (table 2) and children (table 3) [20-22]. Developed with the input of thousands of people with a wide variety of medical conditions, the health care providers who treat them, members of the general population, and extensive literature reviews, the framework is divided into physical, mental, and social health. Each of these major components encompasses multiple subcomponents (eg, the mental health component for adults is comprised of anxiety, depression, anger, positive affect, life satisfaction, meaning and purpose, cognitive function, experience of stress, self-efficacy, smoking, substance use, and psychosocial impact of illness).
An important point is that serious and life-threatening illness can also result in positive outcomes [23,24] such as emotional and spiritual growth, greater closeness with family and friends, and an appreciation of one's inner strength. These psychosocial benefits are included in the Psychosocial Illness Impact – Positive domain of PROMIS [25].
The utility of PROMIS for patient-reported outcomes is discussed further below. (See 'Combined instruments for patient-reported outcomes' below.)
MEASURING HRQL — A vast array of validated and reliable questionnaires are available for assessment of HRQL [26]. They include generic health status instruments, generic illness instruments, and targeted instruments. HRQL instruments comprise the majority of patient-reported outcome measures (PROMs).
Generic health status — Generic health status questionnaires are applicable to all populations and can be completed by individuals both with and without medical illness. These instruments provide benchmarks for comparison across diverse groups, such as healthy and ill populations or different age groups. Examples include the Nottingham Health Profile (NHP) [27] and the Short Form-36 (SF-36) from the Medical Outcomes Study [28,29].
Generic illness — Generic illness instruments are applicable to populations with any medical illness or condition and can be used to compare different illnesses, levels of disease severity, or types of interventions. Such cross-disease comparisons are increasingly important in the allocation of limited health care resources [30]. In addition to measuring general health status, these instruments typically assess the individual's perception of the functional impact of the illness or disability. Examples include the Sickness Impact Profile (SIP) [31] and the Functional Assessment of Chronic Illness Therapy (FACIT) [32].
Targeted — Targeted instruments, often referred to as disease- or condition-specific measures, are designed to assess the HRQL of individuals with specific illnesses (eg, cancer, heart disease, diabetes), specific types of treatment (eg, chemotherapy, lung transplant, palliative care), or symptoms that are specific to some, but not all, conditions (eg, nausea, urinary incontinence). Compared with other types of instruments, these measures provide a more detailed assessment for specific contexts and are also likely to be more sensitive to specific treatment-related changes in HRQL. Examples include the Diabetes Quality of Life instrument (DQOL) [33], the Functional Living Index - Cancer (FLIC) [34], the Functional Assessment of Cancer Therapy-General-7 (FACT-G7), and the European Organization for Research and Treatment of Cancer Quality of Life Core 15-Palliative Care (EORTC QLQ-C15-PAL) [35-38].
One trend in HRQL research is to combine generic and disease-specific instruments in order to fully cover important areas that may impact on HRQL. This has been the standard practice of the FACIT Measurement System [39]. Using the Patient-Reported Outcomes Measurement Information System (PROMIS), for example, universal items assessing physical, mental, and social health were combined with heart failure-specific items to create a comprehensive tool for use in research and patient care [40]. A similar approach has been utilized for patients with osteoarthritis of the knee [41] and sickle cell disease [42].
Combined instruments for patient-reported outcomes
PROMIS — PROMIS [20,21] presents a set of multidimensional HRQL instruments that combine features of the three categories above (table 2 and table 3). PROMIS instruments are applicable across chronic illness populations [43,44]. Item banks for computer adaptive testing and short forms exist for physical function, upper extremity function, pain interference, pain behavior, pain intensity, pain quality, fatigue, sleep disturbance, sleep-related impairment, gastrointestinal symptoms, dyspnea, itch, sexual function and satisfaction, depression, anxiety, anger, alcohol use, smoking, substance use, psychosocial impact of illness, positive affect, life satisfaction, meaning and purpose, cognitive function, self-efficacy for managing chronic conditions, ability to participate in social roles and activities, satisfaction with participation in social roles and activities, companionship, emotional support, informational support, instrumental support, isolation, and global health in adults.
In addition, there are pediatric instruments for physical function (upper extremity, mobility), pain interference, pain intensity, pain behavior, pain quality, fatigue, physical activity, physical stress experience, strength impact, sleep, depressive symptoms, anxiety, anger/irritability, cognitive function, engagement, life satisfaction, meaning and purpose, positive affect, psychological stress experiences, peer relationships, family relationships, social relationships, asthma impact, and global health. Measures can be completed by self-report beginning at age 8 [45] or by a parent reporting on behalf of a child ages 1 to 17 [22,46].
All of the PROMIS instruments were developed using rigorous qualitative [47-49] and quantitative [21,50-52] methods, including use of item response theory, an analytic strategy that allows for the creation of customized short forms and use of a common metric [53]. Although PROMIS instruments have had limited application in palliative care populations [54-57], the breadth of domain coverage suggests utility for research and clinical care in this population as well. This is supported by work demonstrating PROMIS measures predicting survival in patients receiving palliative care [58].
Neuro-QoL — The Quality of Life in Neurological Disorders project (Neuro-QoL), conceptually and methodologically similar to PROMIS, was funded by the National Institute of Neurological Disorders and Stroke to develop and test HRQL instruments that are applicable across the many neurologic conditions. These instruments were initially developed and validated in five adult and two pediatric diseases (stroke, amyotrophic lateral sclerosis [ALS], multiple sclerosis, Parkinson disease, adult and pediatric epilepsy, and the muscular dystrophies) [59-61]. Parallel work extended Neuro-QoL to people with spinal cord injury (SCI-QoL) [62], traumatic brain injury (TBI-QoL) [63], Huntington disease [64], and caregivers for individuals with traumatic brain injuries [65]. The resulting HRQL tools are used in clinical trials [66] and comparative effectiveness research [67]. The common metrics of Neuro-QoL facilitates the comparison of results from clinical trials and other clinical research across conditions.
Proxy or caregiver evaluations of HRQL — There are situations (eg, children, older adults, cognitively impaired patients, end-of-life care settings with a very ill patient) where patient self-reported HRQL must be substituted by proxy assessment. Where it has been studied, there appears to be general agreement between the patient's assessment and that of family caregiver proxies in most [68-73] but not all [74] studies. Also, the possibility of bias related to the subjective burden of caring for the individual must be considered when the proxy is a caregiver [75]. (See "Advance care planning and advance directives", section on 'Surrogate decision-makers'.)
Relatedly, it is also important to consider the quality of life of the family members of people with serious illness. Partners, children, and parents can experience significant alterations in their emotional, social, and even physical wellbeing in response to the illness of a loved one [76,77].
UTILIZATION OF HRQL DATA — Information regarding the impact of an illness or medical condition on HRQL can be put to use in several ways.
Clinical trials — Clinical trials that compare two (or more) treatments often include a HRQL assessment and analysis to help determine overall clinical benefit, particularly when treatment-related side effects are considerable. Compared with the control therapy, the alternative treatment option may be associated with a variety of combinations of relative survival benefit and HRQL. These include:
●Longer survival with better HRQL
●Similar survival but better HRQL
●Shorter survival but better HRQL
●Longer survival but with inferior HRQL
●Shorter survival with an inferior HRQL
Although no individual would purposely select a treatment that results in both shorter survival and a worse HRQL, improved HRQL during therapy may be perceived as sufficiently compelling (particularly during cancer treatment) to outweigh a somewhat shorter survival duration.
Improvement in HRQL as an endpoint in clinical research requires recruitment of sufficient numbers of subjects for a trial to have adequate power. Instruments measuring HRQL with a limited coefficient of variation can decrease the size of a trial needed and offer an important advantage in this regard [78].
Routine collection of HRQL in clinical care — Because HRQL information can provide a detailed assessment of disease and treatment effects, and their global impact on the individual's daily life, routine HRQL assessment with patient-reported outcome measures (PROMs) is increasingly integrated into clinical practice. In this setting, PROMs can serve multiple purposes such as screening for depression or anxiety, monitoring symptoms or outcomes [79,80]. They can also facilitate symptom management and detection of unrecognized problems. For instance, a brief multidimensional HRQL instrument might be administered at every chemotherapy visit. The treating nurse or clinician can then review the current HRQL for indications of problems and compare it with the HRQL from the previous visit. Significant changes can be flagged for follow-up by a provider. A quick glance at a standardized computer-generated printout of HRQL scores and changes from the last visit's scores could catch a problem that might otherwise be missed.
Routine collection of HRQL using PROMs has been shown to be feasible and acceptable to patients and staff and has demonstrated multiple benefits, including improved patient-provider communication, increased patient satisfaction, detection of unrecognized problems, increased actions by clinicians, reduced emergency department admissions and hospitalizations, improved HRQL, and, in two studies, increased survival [81-92]. Several health centers have implemented PROMs across conditions and technologies [91-95].
A systematic review of PROMs data from 16 studies in palliative care, mostly randomized controlled trials with oncology patients, concluded that PROMs improved some care processes (eg, patient-provider communication about symptoms) and some outcomes, including patient and caregiver psychological wellbeing [82]. However, the evidence for an effect on overall HRQL and symptom burden was mixed.
A growing literature identifies the enablers and barriers to implementing HRQL assessment in routine clinical practice [96-102]. Professional organizations (eg, ISOQOL [103], NQF [104], PROTEUS Consortium) and implementation grants (eg, ePROs in Clinical Care [105], HealthMeasures) have generated practical tools.
Predicting treatment response — HRQL data can also be used to predict the outcome of treatment. As an example, in patients with metastatic lung cancer, pretreatment HRQL predicted the likelihood of an objective response to chemotherapy treatment, and the change in HRQL between baseline and six weeks after treatment initiation also predicted survival [106,107] (see "Subsequent line therapy in non-small cell lung cancer lacking a driver mutation"). The importance of this type of information for stratification of patients during random treatment assignment is obvious [108]. This also facilitates the creation of shared decision-making tools when a patient is considering different treatment options [109].
Treatment decision-making in advanced life-threatening illness — Prolongation of life, without regard for the quality of that life, is not a universally desired goal. When considering aggressive, life-prolonging treatments and end-of-life decisions, it is necessary to consider each individual's assessment of what makes life worth living. (See "Overview of comprehensive patient assessment in palliative care", section on 'Illness understanding and care preferences' and "Overview of comprehensive patient assessment in palliative care", section on 'Religious, spiritual, and existential (transcendent) issues'.)
Some patients are willing to consider aggressive and potentially toxic treatments despite slim chances of survival; medical issues do not always constitute the main factors considered. In one series, aggressive therapy was more likely to be accepted among patients with a positive sense of social wellbeing or children living at home [110]. In a second report, 388 older adults were presented with 17 hypothetical decision situations depicting terminal and nonterminal conditions with a very low quality of life and asked to rank the acceptability of several end-of-life options [111]. The majority chose striving to live and seeking active treatment over death, even if they had a poor HRQL characterized by pain, immobility, and extreme dependence on others. Psychosocial variables, including religiosity, values, and fear of death, contributed significantly to the decision-making process, highlighting the complex relationship between HRQL and quality of life. (See 'The influence of nonmedical issues' below.)
For patients with a serious, life-threatening illness, the decision to continue potentially life-lengthening treatment is obviously a very individual one. However, what is also clear is that appropriate palliative care can improve HRQL by reducing symptom burden and decreasing interference with usual life activities. (See "Benefits, services, and models of subspecialty palliative care" and "Overview of managing common non-pain symptoms in palliative care".)
A National Institutes of Health (NIH)-sponsored cooperative research group was founded in 2010 to study treatment-related issues that are specific to the setting of palliative and end of life care [112,113]. The Palliative Care Research Cooperative Group supports clinical trials and other relevant research. For example, one study demonstrated that cessation of statin therapy in terminally ill patients is safe and may improve quality of life and reduce cost [114]. (See "Palliative care: The last hours and days of life", section on 'Eliminating non-essential medications'.)
In addition, the measurement core of this group maintains a published library of recommended instruments to measure patient-reported outcomes and quality indicators in palliative care [115].
Evaluation of quality of health care — The evaluation of health care quality has largely utilized measures that assess the process of care. These performance measures can include assessments, such as the proportion of providers that conduct a foot examination in diabetic patients, or recommend or prescribe an indicated treatment for a specific condition. Increasingly, payers and providers are interested in additionally utilizing HRQL measures that capture outcomes of care. Patient-reported outcome performance measures (PRO-PMs) include assessments such as the level of patient-reported depressive symptoms, degree of physical function, pain, and sleep quality. Guidance for the development, evaluation, and maintenance of performance measures generally [116,117], and PRO-PMs specifically [118,119], has been published. The methodological issues related to the selection, administration, and use of PRO-PMs, including generic versus disease-specific PROs, process (eg, assessment of depressive symptoms) versus outcome (eg, level of depressive symptoms) measures, and risk adjustment, are beginning to be better understood [15,118-120].
CHALLENGES IN HRQL RESEARCH — Despite the progress in HRQL research over the last four decades, several challenges remain. These include the identification of what constitutes clinically significant differences and meaningful changes in HRQL, the development and testing of conceptual models linking medical and psychological variables to HRQL [121], and the validation of existing item banks and computer adaptive tests as measures of HRQL that enable comparison across diseases and treatments.
Defining a clinically meaningful change — What degree of change in HRQL is of sufficient magnitude to warrant a treatment modification by the clinician? Identifying changes in HRQL that are clinically significant involves determining whether the change that is observed in response to an intervention is meaningful and important, or statistically significant yet clinically irrelevant [122-124].
For patients with progressive conditions, such as many of the neurologic disorders, even stable scores can be clinically meaningful, since they can indicate the avoidance of decline or loss of function. For example, maintaining the ability to move a finger can mean that an individual can operate an electric wheelchair, while maintaining the ability to swallow means that an individual can still eat and drink [125]. This highlights the significance of incorporating patient and caregiver input, utilizing instruments that are sensitive to very small score changes, and prospectively defining clinically meaningful outcomes in both research and practice.
One approach to answering this question is to compare changes in HRQL scores with global ratings of change in different life dimensions [126] or in life stress units [18]. As an example, in one report, an important difference (ID) was defined based on patients' global ratings of change and applied to three studies measuring dyspnea, fatigue, and emotional function in patients with chronic heart and lung disease [126]. The ID was represented by a mean change in score of approximately 0.5 per item on the HRQL instrument, when responses were presented on a 7-point Likert scale.
Complementary approaches to this question have received considerable attention. For example, clinically important differences or changes can be calculated by comparison of HRQL score differences or changes to parallel differences or changes in meaningful anchors, such as the patient's global rating of change mentioned above or clinical measures relevant to a given condition (such as tumor response in oncology or hemoglobin change in anemic patients). Other important HRQL anchors used in oncology, for example, include disease stage/severity, treatment status, progression-free survival, and performance status.
Distribution-based methods calculate an ID by applying a criterion of one-third to one-half of the pooled standard deviation, or, alternatively, the standard error of measurement, of the measure at the baseline assessment. Results from several studies indicate that similar estimates are obtained regardless of the method used [127-129]. In part because of this, the widespread use of a standard deviation to define meaningful group differences across HRQL measures has been popular [130]. Although this may be useful as a starting point for clinicians who are not familiar with particular HRQL measures, more credible estimates can be obtained through the use of anchors that are sufficiently correlated with the target HRQL measure. Indeed, multiple methods for deriving a range of recommended IDs may be most appropriate [131,132].
Another approach to aid in clinical interpretation of HRQL scores has been to identify meaningful cut-points (eg, the threshold at which time a clinician may consider a referral for emotional distress or modification of pain medication) [133]. The successful establishment of meaningful cut-scores for symptoms (eg, mild, moderate, or severe) has been demonstrated in cancer patients [134,135], patients with serious neurologic conditions [136], patients with rheumatic disease [137,138], patients with spinal cord injury [139], and pediatric patients with juvenile idiopathic arthritis [140]. Unlike IDs, this approach recognizes that a change in score may have different meanings depending on where in the range of scores it takes place. For example, the meaningfulness of a decrease in pain is dependent on the baseline pain level, with a larger decrease required for meaningfulness with a higher starting pain level [141] in pain scores is required for meaningful change.
To summarize, evaluating the clinical meaningfulness of a HRQL score or change has great significance for patients, clinicians, payers, and regulators. Recommendations suggest that more appropriate and precise definitions can be obtained through a triangulation of multiple approaches, such as those outlined above, and sophisticated analytic strategies [142].
Palliative care patients — Defining a clinically meaningful change can be particularly challenging for palliative care patients. People living with chronic, life-threatening illness often progress through specific phases of clinical worsening and increasing physical, mental, and social challenges. Furthermore, when people are severely ill or disabled, it can be difficult to simply obtain reliable responses to a long set of questions. For this reason, many have abbreviated questionnaires for use in end-of-life studies [36].
However, disease progression is often accompanied by a shift in priorities or life goals of the patient and family [16,143]. When this happens, it can have an effect on responses to self-report questionnaires about symptoms and functional abilities. Often, social, family, and spiritual issues become more important than they were previously. In fact, this sometimes results in the counterintuitive finding that overall quality of life is maintained, or even improved, even in the face of worsening physical symptoms and functioning [144].
There are suggestions for measuring these emerging issues and how they might modify the value people place on what is clinically meaningful. For example, specific questions can be added to existing measurements such as the Functional Assessment of Cancer Therapy (FACT) and Functional Assessment of Chronic Illness Therapy (FACIT) [145-147]. Another instrument, the Quality of Life at the End of Life instrument (QUAL-E), includes the domains of life completion and preparation for the end of life [148].
In addition, there have been many efforts to individualize HRQL to the individual, including tailoring the questions that are asked, weighting individual questions or domains for their relative importance to the patient, or allowing patients to select their most important concerns and tracking them over time. Unfortunately, this has proven difficult to implement; limited investigations suggest that weighting has little additional predictive value [149], and there are legitimate concerns about comparing one person's individualized score with that of another. Nonetheless, several such individualized instruments are available, including the Patient-Generated Index [150] and the Schedule for the Evaluation of Individual Quality of Life [151].
The influence of nonmedical issues — A second challenge is to develop and test models of non-illness-related factors (eg, psychological, social, cultural, and economic issues) that might influence the impact of a particular level of impairment on HRQL. In one model, the amount of distress and dissatisfaction experienced by the patient as a result of the symptoms and functional limitations induced by illness and its treatment is influenced by individual factors, sociocultural influences, and available resources [108]. Other proposed models relate physiological variables, symptoms report, and physical functioning to overall HRQL [152]. Evaluation of these interrelationships is critical to an understanding of what influences HRQL and the potential for modifying these factors through targeted interventions.
Language and culture — The nature of self-reported symptoms, function, and quality of life is such that perspectives and reporting are influenced by language and culture. Therefore, it is important when developing questions that their meaning is comparable across different languages and cultures. This is best accomplished through thoughtful writing of concepts so that they are easily translated, and then use of a translation methodology that checks and evaluates cross-cultural relevance and understandability. In some cases, simultaneous development of multiple language versions has been found to be an effective way of increasing comparability across languages and cultural groups. When multiple language versions are used in one study, if sample size permits, evaluation of the performance of each item relative to the others, language-by-language, can also be done. This is referred to as checking for differential item functioning (DIF) by language or cultural group. (See "Cultural aspects of palliative care".)
Personality and individual differences — Psychological characteristics such as optimism/pessimism, neuroticism, depression, and social desirability can influence the overall "tone" of an individual's response to questions. Typically, this is managed as a constant, underlying variable that is generally controlled within-person in a longitudinal change score, and balanced across groups when respondents are randomly assigned. Nevertheless, caution regarding personality influences on reporting is warranted.
Spiritual and existential wellbeing — Spiritual wellbeing has been defined as a sense of meaning, peace, and connectedness with something larger than oneself [146]. In the face of life-threatening illness, spirituality is often seen as a particularly effective resource for coping with physical symptoms and functional limitations. Conversely, spiritual distress or conflict can be particularly problematic, especially if it is prolonged. With a patient's agreement, chaplains, religious leaders, or spiritually attuned health care providers of many types can assist the patient in exploring sources of distress and resolution. (See "Overview of spirituality in palliative care" and "Influence of spirituality and religiousness on outcomes in palliative care patients".)
Existential distress ("Why me?", "What does my life mean if it might end soon?") can negatively affect HRQL to an extent similar to physical symptoms, such as pain. Some HRQL assessments, notably the McGill Quality of Life Questionnaire [153] (and its revised version [154]), include an existential wellbeing subscale. As an example, respondents rate whether they have been able to achieve their goals, whether life is worthwhile, and the extent to which every day feels like a burden or a gift. Also, at least one investigator has begun to document the positive effect of an intervention called "meaning-centered psychotherapy" specifically to address the existential questions and distress that can be wrought by a fatal illness [155,156]. (See "Overview of comprehensive patient assessment in palliative care", section on 'Religious, spiritual, and existential (transcendent) issues' and "Overview of spirituality in palliative care" and "Psychosocial issues in advanced illness", section on 'Common issues for patients with advanced illness'.)
HRQL and psychology — Despite the importance of HRQL research to health and the delivery of medical care, its value is not widely appreciated or recognized within the field of psychology. Fewer relevant publications appear within the psychology literature, despite the rapid growth of the field over the last 20 years. One possibility is that the focus on HRQL as an outcome indicator for medical illness and its treatment has forced the publication of pertinent studies in the medical rather than psychology literature.
Additionally, the field of psychology has made valuable contributions to the field of HRQL research. The development of valid and reliable instruments to measure the patients' perspective of their illness and treatment was made possible by the demonstration of their psychometric properties; this is largely the work of psychologists. There are now published clinical trials examining the impact of psychologic and/or pharmacologic treatment on various psychiatric diagnoses, including schizophrenia [157,158], major depression [159,160], bipolar disorder [161], and posttraumatic stress disorder [162]. In addition, significant attention is being paid to routine monitoring of patient outcomes as a tool to improve psychotherapy effectiveness [163-165]. With the increasing emphasis on the evaluation of HRQL among populations with mental illness [152,166-168], it appears likely that the next decade will witness a growing recognition of HRQL research by psychology, as the past decade has shown its growth within medicine and health care in general.
SUMMARY
●Context – Quality of life is comprised of broad concepts that affect one's overall life satisfaction. For matters related to health, quality of life has been applied specifically to those life concerns that are most affected by health, illness, or treatment. The term "health-related quality of life" (HRQL) is used for this purpose. (See 'Introduction' above.)
●Definition – A definition of HRQL is "the extent to which one's usual or expected physical, emotional, and social wellbeing are affected by a medical condition or its treatment." This definition incorporates the two widely accepted aspects of quality of life: subjectivity and multidimensionality. (See 'Defining HRQL' above.)
●Measurement – A vast array of validated and reliable questionnaires or patient-reported outcome measures (PROMs) are available for assessment of HRQL in patients with a serious life-threatening illness, including generic health status instruments, generic illness instruments, disease-specific instruments, and combined instruments such as the Patient-Reported Outcomes Measurement Information System (PROMIS) (table 2 and table 3). (See 'PROMIS' above.)
●Application – There are several areas where HRQL information is of value in medical care; examples are as follows:
•Clinical trials – Improvement in HRQL as an endpoint in clinical research. (See 'Clinical trials' above.)
•Clinical care:
-As a tool for assessing the efficacy and tolerability of treatment, capturing changes in clinical status during treatment that might otherwise be missed, and evaluating the need for further assessment, treatment, rehabilitation, or palliative care. (See 'Routine collection of HRQL in clinical care' above and 'Predicting treatment response' above.)
-As an aid to decision-making in patients who are faced with aggressive, life-prolonging treatments and end-of-life decisions. (See 'Treatment decision-making in advanced life-threatening illness' above.)
-As a means of documenting quality of care based on improvement or maintenance of patient-reported outcomes. (See 'Evaluation of quality of health care' above.)
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