Doctors use measures in long-term diseases like rheumatoid arthritis to assess how well patients are doing, and if their disease is getting worse. These measures can help doctors to decide if medicines are working, and if patients are receiving the right treatment.
INTRODUCTION
Rheumatoid arthritis is a chronic inflammatory disease that affects a person’s joints, causing pain and disability. The severity of the disease usually increases the longer it goes on as joint damage is often irreversible. Many studies have suggested that treatment and interventions should target disease in the early stages to help prevent long-term damage to the joints. There are a lot of different measures and tools that are used by researchers in clinical trials and by doctors to assess disease severity and the impact it has on a patient. Disease activity measures look at how the disease is progressing, and often include levels of certain markers in the blood, joint counts or a combination of several measures into an index. Functional measures look at things like pain, sleep or quality of life, and are often assessed using questionnaires rather than practical tests. Improving physical function is one of the most important goals for patients, but it may not always be as representative of what is happening in the joint as X-rays or disease activity measures.
WHAT DID THE AUTHORS HOPE TO FIND?
The authors performed this study to see whether the disease activity and functional measures that are used in rheumatoid arthritis can be used for every patient, or whether there might be a difference seen depending on the stage of a patient’s disease. Previous studies have suggested that functional measures are not as useful in patients with long-standing rheumatoid arthritis, compared to patients with the disease in its early stages. It is thought that this might be because too much damage has already occurred in the joints of patients who have had the disease for a long time.
HOW WAS THE REVIEW CONDUCTED?
A pooled analysis takes the results from several sources and combines them in order to try to answer a new question. In this review, the authors took data from several clinical trials done in patients who had suffered from rheumatoid arthritis for at least 3 years. These trials had originally been performed to evaluate how well a variety of medicines work in rheumatoid arthritis. The collected data were then split into two groups. The first group contained patients who had received a single type of medicine called a disease-modifying antirheumatic drug – such as methotrexate or leflunomide. The second group had received a disease-modifying antirheumatic drug plus a TNF inhibitor. TNF inhibitors are a class of medicines known as ‘biologics’ which target particular causes of inflammation in the joint. For each of these two groups, the authors then calculated how the length of a patient’s disease affected the response to the disease activity and functional measures used.
WHAT DO THE RESULTS SAY?
The results found that almost all of the functional measures commonly used by doctors become less accurate the longer a patient has had their disease – so although physical function is an important goal of treatment, it is not a reliable measure for disease activity.
In patients with earlier disease there was a chance that 6 in every 10 patients would show a functional response to treatment, but this decreased to only 3 in every 10 patients in late disease. The same effect was not seen for disease activity measures, which correlated in both early and late disease. The authors say this means that disease activity measures are accurate at any stage of a patient’s disease. There was no difference seen between the two treatment groups to suggest that the treatment patients were receiving had an effect on their responsiveness to functional or disease measures. This means that the findings apply no matter which medicines patients are taking for their rheumatoid arthritis. This study might be important for doctors when they compare results between different trials or medicines in patients with different stages of disease.
HOW RELIABLE ARE THE FINDINGS?
The findings rely on clinical trial data, and the patients included in these can be very different from the ‘normal’ patients that a doctor might see in their clinic. Partly this is because there are very strict inclusion rules for trials, which may mean that patients with certain other conditions or diseases or those outside certain age ranges may not be able to enter them. Patients in clinical trials may also attend more follow up visits and have more testing done than normal patients outside a trial. But the authors are confident that the types of patients included in this review are suitable for testing the effect of disease duration on functional responses, and that the findings apply to real patients. Because the data included come from several trials conducted by different companies and with different drugs, there is no risk of bias towards any particular outcome. Also, the spread of data across these trials means that the assessments have been done by many different people, and this limits the risk that one person or clinic may be applying a measurement incorrectly.
WHAT DOES THIS MEAN FOR ME?
For patients with established or late rheumatoid arthritis it may not be possible to achieve treatment goals based on functional outcomes, but they can still respond to treatment, and this can be assessed using measures of disease activity. The authors recommend that aiming to improve disease activity should remain the main target when treating rheumatoid arthritis, with functional improvements as a secondary aim. This might mean that doctors treating patients with rheumatoid arthritis use disease activity goals rather than functional goals.
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Date summary prepared: March 2015
Summary based on research article published on: 15 January 2014
From: Aletaha, D. et al. Chronicity of rheumatoid arthritis affects the responsiveness of physical function, but not of disease activity measures in rheumatoid arthritis clinical trials. Ann Rheum Dis 2015;74:532–37. doi: 10.1136/annrheumdis-2013-204015
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