Quality of life and the outcome of established rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA) is a long-term condition causing joint pain and swelling and sometimes systemic involvement. The aims of treatment are, first, to reduce the impact the disease has on a patient and, second, to halt progression of disease. The advent of intensive therapy, including biologics, has led to a major improvement in outcome.

To assess treatment impact, formal outcome measures have been developed. Traditionally, these focussed on the clinical aspects such as disease activity and joint damage. More recently, there has been an increased focus on patient-related outcome measures including quality-of-life measures. These enable illness evaluation from patients’ perspectives, examination of care quality and comparison of the effectiveness and cost-effectiveness of treatment.

This article examines advantages and disadvantages of the various outcome measures which are generally used in RA, with a focus on quality of life and patient-related measures.

The natural history of disease is defined as the way in which the condition develops in affected patients over time without treatment. In current Western medical practice, where most patients receive some form of treatment, the crucial question is usually not about examining untreated natural history but to assess whether natural history is further improved by new treatments as compared to standard treatment. An additional complexity for long-term conditions is that, because disease progression may extend over many years, the assessment of treatment-related changes in natural history is often not directly practicable. Instead, the focus has to be on assessing the impact of new versus conventional treatment over a short period by measuring the patient’s state of health before and after treatment.

Accurate measurement of a patient’s state of health requires the use of a variety of clinical outcome measures which broadly reflect the impact of the relevant condition on the patient’s health. The traditional focus of clinical outcome assessment has been physician-oriented, measuring changes in disease-specific symptoms, signs and investigation findings. However, the importance of the patient’s perspective on disease impact has been increasingly recognised leading to the development of patient-related outcome measures (PROMs) and the routine measurement of quality of life. These constitute the main focus of this chapter.

Finally, the measurement of disease impact has been extended to the calculation of treatment benefit in terms of quality-adjusted life years (QALYs) ; this information can be used in cost–utility analysis to help make decisions about resource allocation at a societal, group or individual level. This will be alluded to briefly in the chapter.

Assessing clinical outcome in rheumatoid arthritis

The ultimate outcome for us all is death and, in many diseases such as cancer, death rates are an appropriate, if crude, indicator of clinical outcomes. However, in long-term diseases such as rheumatoid arthritis (RA) death rates are of limited value, as deaths are infrequent and, at the individual patient level, not necessarily clearly directly related to RA or its therapy.

In RA, the key outcome measures focus on three inter-related domains. The first domain reflects the extent and severity of the underlying inflammatory process. In patients with RA, this means the clinical and laboratory assessment of the presence and severity of joint inflammation. The second domain is end-organ damage. In RA, this primarily means the extent and severity of joint damage, although damage from co-morbidities, such as lung or cardiovascular disease, may also need to be considered. Finally, and most importantly, the third domain assesses the way in which disease affects patients’ quality of life. Such assessment of quality of life is usually made by patients themselves (thus falling into the category of a PROM) and needs to reflect the multiplicity of ways in which their RA has impacted on their lives.

Requirements of good outcome measures

Outcome assessments need to be both reliable and valid. This means they need to record measures in a reproducible way and that they genuinely measure what they claim to record. Some outcome measures are categorical. Death is a simple binary outcome (alive or dead). Other categorical measures divide patients into a few categories; the classical example was the Steinbroker functional index, which divided patients into four classes. However, most outcomes are numeric scales. Examples include joint counts, X-ray scores and quality-of-life measures including the health assessment questionnaire (HAQ) and the Medical Outcomes Survey Short Form 36 (SF-36) .

Another key domain to be taken into account is the effect of time. Short-term outcomes over weeks and months are easier to assess than long-term outcomes which extend over years or even decades. These long-term outcomes are of critical importance to patients. Usually, clinical trials focus on short-term outcomes, whilst observational studies explore longer-term outcomes.

Complexities in using outcome measures in RA

The first complexity is to identify the optimal set of outcome measures for RA. As in many other diseases, RA clinical outcomes are closely inter-related. Patients who have reduced synovitis also have less joint damage and better quality-of-life measures and vice versa. As a consequence, it is not essential to measure all relevant outcomes. Instead, a few carefully chosen outcomes can provide a comprehensive picture of the impact of treating RA. However, there is currently debate about exactly what outcomes should be collected. As an extension of this issue, appropriate outcomes measure will change over time. For example, in RA, the wider availability of very much more effective treatments in the last 10 years has meant that outcomes once considered aspirational are now routinely reached, for example, remission or low disease activity states.

A second problem is that, as well as treatment, multiple other factors can impact on the outcome of RA including fixed demographic features such as gender, age, ethnicity and deprivation. Invariably poor, elderly women from minority ethnic groups will have worse outcomes than wealthy, young Caucasian men. This variability makes it very challenging to compare outcomes across units as they all have somewhat different local populations. Inner-city hospitals in deprived areas will have worse outcomes than hospitals in wealthy areas. Although there is usually improvement with treatment, there can also be adverse events leading to a deterioration of health.

In addition to these fixed factors, other aspects of patients’ health have major impacts on their clinical outcomes. Lifestyle factors (notably smoking) impact on both disease outcome and response to treatment. Major co-morbid physical and psychological illnesses are a crucial issue to take into account as patients with multiple medical disorders will have reduced quality of life compared to patients who only have RA. Finally, patients’ health beliefs and their cultural backgrounds have major impacts on quality of life. Patients who believe they have a serious medical problem will find their beliefs fulfilled. This issue inter-relates with ethnic differences and together these are challenging issues to resolve. Currently, there is little emphasis on changing patients’ health beliefs to improve RA outcomes, but it is likely that this may be as effective as many medical interventions.

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