According to a new study, blood tests used to diagnose and monitor rheumatoid arthritis may be inaccurate if the patient happens to be an obese woman. This makes it harder to track the progression of the disease, as the signs of rheumatoid arthritis become obscured by the bodily changes associated with obesity.
“Physicians might assume that high levels of inflammation mean that a patient has rheumatoid arthritis or that their rheumatoid arthritis requires more treatment, when in fact, a mild increase in levels of inflammation could be due to obesity instead,” explained study author Dr. Michael George, who’s with the University of Pennsylvania Health System in Philadelphia.
The diagnosis of rheumatoid arthritis often includes multiple tests, including blood and imaging tests. C-reactive protein (CRP) and erythrocyte sedimentation rates (ESR) are common blood markers that indicate inflammation in the body, of which rheumatoid arthritis contributes to. However, these are often considered non-specific markers, as many unrelated processes can cause them to increase. Therefore, CRP and ESR often support the diagnosis of rheumatoid arthritis, but additional testing is usually required.
By looking at inflammatory markers in the blood—CRP and ESR—researchers can determine the severity of the RA case. However, previous studies show that obese patients, especially women, could have higher levels of CRP and ESR in their blood streams, complicating the diagnosis. They wanted to take a closer look at this issue as it may confound results.
The study in question included information from more than 2,100 people with rheumatoid arthritis, and they compared that to data from the general population. They found that a higher body mass index (BMI) was associated with greater CRP levels in women with rheumatoid arthritis and in women of the general population who were severely obese. The researchers also looked at ESR levels and found a modest association with obesity as well.
Not to be excluded, men were also looked at in this investigation. The researchers found that men with rheumatoid arthritis and a lower BMI were associated with greater CRP and ESR levels.
The relationship between CRP and ESR levels and rheumatoid arthritis are known to be correlated, but these new findings help us understand the link between the markers for inflammation and weight, in addition to sex differences. What can be concluded is that obese women may see the same increases in inflammatory markers as those seen in rheumatoid arthritis. They hope that physicians will keep this association in mind when making a diagnosis of the disease in future patients.