Measuring Rheumatoid Arthritis Disease Activity

Tags: Nuclear bone scan, Patient reported outcome measure, Rheumatoid Arthritis test

Did you ever go to the store for milk and bananas? And come home with frozen pizza and ice cream? Sometimes I spend a couple of hours looking for something and discover something else that’s worth bringing back to you. That’s how I found this ten year old article about the dilemma of measuring Rheumatoid Arthritis activity.

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Differing perspectives on measuring Rheumatoid Arthritis disease activity

But first, who cares? You either have Rheumatoid Arthritis or you don’t right? Once you have a diagnosis, why measure anymore? That is how some doctors reason and there’s some advantages to it. The patient gets treated with DMARDs and less money is spent testing.

As patients report frequently here on the blog, there are plenty of rheumatologists who go to the other extreme. They “treat by the tests.” If lab results are in normal range, the patient is told that the disease activity is “controlled,” or even in “clinical remission.”

Doctors may produce a type of disease activity score (DAS) from counting certain joints or may rely on a variety of methods to assess disease activity including blood tests, x-rays, or patient questionnaires. If you are not an RA patient, that sounds pretty straightforward. But if you have RA or if you’ve read many of the comments on this blog, you know it’s much more problematic.

Blood test results are commonly normal even in patients with painful symptoms and continuing RA damage.
DAS joint counts can be subjective. Studies show doctors consistently rate disease activity as lower than patients do.
Ultrasound imaging may not reliably monitor Rheumatoid Arthritis activity because of variability of equipment and subjectivity of technique.
When x-rays do show damage, it is only in retrospect. Plus they only reflect bone damage while RA affects soft joint tissues, veins, arteries, or organs.

Difficulty of measuring Rheumatoid Arthritis disease activity is not new

Ten years ago, some Canadian researchers seemed to understand our predicament perfectly. I found it astonishing to read this old study about near‐infrared spectroscopy (NIR):

“Although RA has traditionally been thought of as one homogeneous disease, it has become increasingly obvious that there are many subgroups within this spectrum… Certain early prognostic features of patients are suggestive of more aggressive disease. These include specific genetic haplotypes, female gender, high rheumatoid factor titres, multiple joint involvement and early erosive damage. However, no single feature predicts the severity of disease or the extent of involvement at a specific joint… Determining synovial involvement is often complicated by the discordance that is commonly found between the detection of swelling, tenderness and temperature of a joint with the plain radiographic assessment, which may not yet show any underlying damage… Some studies, although using more invasive techniques with biopsies and magnetic resonance imaging, suggest that the clinical perception of joint involvement may be underestimated and quite inaccurate. It is therefore important to try to find modalities to detect early changes that are accurate and easy to perform.” (Emphasis added.)

What hope is there for measuring Rheumatoid Arthritis disease activity?

Those statements sound like they came from this blog. It does astonish me how few seem to understand these points a decade later. Science will catch up with RA eventually. The near-infrared spectroscopy did not become a standard technique and I cannot find recent studies using it. Does anyone know why? The nuclear bone scan (scintigraph) is another method that we hear about periodically. Stay tuned for more on that one very soon. That’s what I went to the store for in the first place.