Obesity in women may interfere with the diagnosis and monitoring of rheumatoid arthritis (RA) through blood tests, according to a new study. Researchers call for more attention to the obesity factor when analyzing results of blood tests in female patients with RA.
The study, “The Impact Of Obesity And Adiposity On Inflammatory Markers In Patients With Rheumatoid Arthritis,” was published in the journal Arthritis Care & Research.
The level of inflammation in the body can be detected in blood tests for C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR). These biomarkers are also useful to diagnose RA and assess the response to a given anti-inflammatory treatment.
However, previous studies have shown that obesity may itself increase the levels of CRP and ESR. This prompted Michael George, MD, and his research team to investigate whether obesity could interfere with the diagnosis of inflammation using blood tests.
In the study, researchers evaluated the association between body mass index (BMI) with CRP and ESR in two groups of RA patients: the Body Composition (BC) cohort (451 patients) and the Veterans Affairs Rheumatoid Arthritis (VARA) registry (1,652 patients).
Results showed that women with RA who have greater BMI had greater levels of CRP, especially those with severe obesity. The association between obesity and ESR in these patients was more modest.
In men with RA, however, a lower obesity level was associated with greater CRP and ESR, compared to the positive associations found in men in the general population.
“Obesity is associated with greater CRP and ESR in women with RA,” researchers wrote in their article. “This association is related to fat mass and not RA disease activity.”
“Our results suggest that obesity may lead to increased levels of CRP and ESR in women with rheumatoid arthritis,” George said in a news release. “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 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,” George concluded.