A group of researchers from the University of Pennsylvania Health System obesity may impact blood tests that are utilized for diagnosing and monitoring rheumatoid arthritis (RA) in women. Blood tests for erythrocyte sedimentation rate (ESR) and C-reactive protein (CPR) are utilized to assess levels of inflammation in the body. The tests are also utilized to determine how effective treatments are working for specific patients.
Several published studies have discovered links between greater body mass index (BMI) and ESR and CRP. Michael George, MD MSCE, of the University of Pennsylvania Health System and his colleagues sought to determine the extent to which obesity biases these markers. The research team compared data on 2,103 participants with arthritis to data from the general population.
Among women in the general population and women with RA, greater BMI correlated with greater CRP, especially among the women with severe obesity (BMI of >40 kg/m2). The connection was seen in men in the general population, but the link between inflammation and obesity were disparate in men with RA. In these people, a lower BMI correlated with a greater ESR and CRP. This discovery might be essential for understanding the link between inflammation and weight and how it may differ between women and men.
“Our results suggest that obesity may lead to increased levels of CRP and ESR in women with rheumatoid arthritis,” said Dr. George. “The increase in these levels of inflammation was not because rheumatoid arthritis was worse in these women. In fact, we found that obesity leads to very similar increases in these lab tests even in women without rheumatoid arthritis.”
Physicians should be extremely careful when interpreting C-reactive protein and erythrocyte sedimentation rate tests, since obesity and rheumatoid arthritis can contribute to levels of inflammation. “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,” he explained.
The findings were published in the journal Arthritis Care & Research on April 10, 2017.