Adapting the thresholds in the Boolean remission definition would improve patient evaluation.
Introduction
Rheumatoid arthritis is a chronic inflammatory disease that can affect a person’s joints, and may cause pain and disability. Rheumatoid arthritis affects people of all ages, and is more common in women than men.
The goal of treatment for rheumatoid arthritis is to achieve state of remission, meaning the absence of disease activity (no active signs or symptoms). There are two recommended ways to measure whether someone is in remission:
● The first is called ‘Boolean remission’. This looks at four components including joint swelling and tenderness, markers of inflammation in the blood, and how well the patient themselves thinks they are doing. Each item has a cut-point of 1. This means that patients are defined as being in remission only if none of these four measures exceeds 1. Each item has a different range – for example, up to 10 for patient well-being, and up to 68 for the number of painful joints.
● The second is the simplified disease activity index (often shortened to SDAI). This uses five components – similar to those in the Boolean tool, but with an added component of how well the treating doctor thinks the patient is doing. However, instead of having a cut-point for each item, they are first added together and the threshold relates to the sum. This means that an individual component may be slightly higher than 1 as long as the sum of the five does not exceed the threshold for remission – which has been determined to be a maximum of 3.3.
Research has shown that the thresholds of 1 for the patient’s well-being in the Boolean remission definition may not work for a lot of people, even if they have no joint swelling or tenderness.
What did the authors hope to find?
The authors hoped to find out what would happen if the threshold for patient well-being in the Boolean remission tool was changed. They wanted to see whether increasing the threshold for the patient-reported component in the Boolean definition would tally better with the SDAI results, and whether it would be safe to do this,
without risking joint damage or disability for people over a long period.
Who was studied?
The study looked at 2600 people with rheumatoid arthritis who had taken part in one of six previous clinical trials to test TNF inhibitors. In total, 1680 people had early or new disease, and 920 had more established long-term disease.
How was the study conducted?
This was a retrospective study, which means that the authors used existing data to look back and find people for each group.
Using the data, the authors looked to see what would happen to the scores if they changed the definition of Boolean remission by increasing the patient-reported assessment information (Patient Global Assessment, or PGA) from a cut-off of 1 up to 3, or if they left it out. They then used statistics to estimate how well the modified Boolean remission definitions lined up with the SDAI definition. Finally, they looked at X-rays and functional outcomes in people after 1 year of treatment, and compared the results in people who were classed as being in remission at 6 months according to the new modified definition.
What were the main findings of the study?
The first finding was that increasing the PGA cut-off values increased remission rates in both early and established rheumatoid arthritis. The bigger the cut-off, the more people were classed as being in remission. The best agreement between the two tools was when the PGA was between 1.5 and 2.
When they looked at the 1-year outcomes, there was a small decline in function for every 0.5 increase in the PGA, but this was minor. But completely removing PGA from the Boolean remission definition had a significant impact on functional outcomes at 1 year. There was no difference in X-ray outcomes.
Are these findings new?
Yes, this is the first time that anyone has looked at the best cut-off for PGA in the Boolean remission criteria, and shown how to achieve a large overlap with SDAI without compromising good long-term clinical and radiologic outcomes. It also proves that taking the patient’s own reports out of the remission definition increases the
chance of worse functional outcomes.
What are the limitations of the study?
Although the study was conducted using a large set of patients with different disease duration, most of the data were more than 10 years old. This might explain why patients showed quite high rates of radiographic progression over 1 year, since at trial entry patients had high disease activity, which is less common these days.
What do the authors plan on doing with this information?
The authors suggest that ACR and EULAR look at the cut-offs in their Boolean remission tool, and consider changing the PGA to 2.
What does this mean for me?
If you have rheumatoid arthritis, you will benefit from a definition of remission that is accurate and is consistent no matter which tool your doctor uses to measure it. In the future, the way remission is worked out might be different.
If you have any concerns about your disease or its treatment, you should talk to your doctor. It is important that you do not stop taking any medicine you have been prescribed without getting proper medical advice.
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Date prepared: March 2020
Summary based on research article published on: 5 February 2020
From: Studenic P, et al. Testing different thresholds for patient global assessment in defining remission for rheumatoid arthritis: are the current ACR/EULAR Boolean criteria optimal? Ann Rheum Dis 2020;79:445–452. doi:10.1136/annrheumdis-2019-216529
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