Weight Among Women Impacts Rheumatoid Arthritis Blood Tests, Study Suggests

Obesity in women may influence the results of blood tests used to diagnose and monitor rheumatoid arthritis (RA).

Blood tests for C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) help examine the levels of inflammation in the body. Physicians may use the test to diagnose RA and to determine the efficacy of treatment.

Prior studies have shown a link between higher levels of CRP and ESR with greater body mass index (BMI). In a study published inArthritis Care & Research, the investigators sought to determine the extent to which obesity biases these markers.

The investigators analyzed data from 2103 patients with RA and compared them with data from the general population.

The results of the study showed that greater BMI was associated with greater CRP in both women with RA and in the general population, especially among women with severe obesity. The findings also showed a modest association betweenobesityand ESR in women.

Although the associations were also observed in men in the general population, the link between obesity and inflammation was different in men with RA. In this population, lower BMI was associated with greater CRP and ESR.

The findings highlight the importance between understanding the relationship between BMI and inflammation and how it may differ among men and women, according to the investigators.

“Our results suggest that obesity may lead to increased levels of CRP and ESR in women with rheumatoid arthritis,” said author Michael George, MD, MSCE. “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 with rheumatoid arthritis.”

Dr George stressed that physicians should err on the side of caution when interpreting the blood tests because RA and obesity 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,” Dr George concluded.