Evaluating the Presence and Impact of Comorbidities in Rheumatoid Arthritis

Comorbidities are common in patients with rheumatoid arthritis (RA), and the presence of comorbidities reduces the chance of remission and is associated with worse functional status and disease activity measures. Two abstracts presented at the European League Against Rheumatism (EULAR) analyzed prevalence and impact of comorbidities in RA.

In the first, researchers from Argentina used a descriptive cross-sectional study to determine the prevalence of comorbidities in RA and evaluate associated variables.¹ They included 345 patients and the presence of comorbidities was evaluated using the Rheumatoid Arthritis Comorbidity Index (RACI) and the Disease Comorbidity Index (RDCI).

RACI consists of 31 comorbidities groups in 11 categories, while RDCI consists of 11 comorbidities. The score range for RACI is 0-36, and the RDCI score range is 0-9. For both, a higher score indicates greater comorbidity.

Using RACI, nearly all (90.3%) patients with RA had some comorbidity measured, and 73.3% had more than 1 comorbidity. Patients with more than 1 comorbidity had a higher Health Assessment Questionnaire score and age. With RCDI, less than half (47.2%) of cases had some comorbidity. Patients without comorbidity by RDCI had at least 1 comorbidity by RACI.

In the second abstract, the authors used RDCI to better understand the role of comorbidities in treatment outcomes.² They evaluated 251 patients in an observational retrospective study. Most of the patients had very high or high disease activity at baseline and they were being treated with a first-line biologic disease-modifying antirheumatic drug (bDMARD). Nearly all (90%) were concomitantly using corticosteroids and/or other disease-modifying antirheumatic drugs.

Cardiovascular disorders were by far the most frequently reported comorbidity (37.5%) followed by osteoporosis (7.6%), and depression (6.8%). Nearly two-thirds (63.6%) had at least 1 comorbidity.

After stratifying patients into 4 subgroups by RDCI score, the authors found that the mean age increased as the RDCI score increased. RDCI was also strongly correlated with the number of comorbidities. RDCI was poorly correlated with C-reactive protein, patient global assessment of disease activity, and Health Assessment Questionnaire Disability Index.

At 12 months, the Disease Activity Score-28 remission rate was 37.8%, 6.7% of patients achieved a good EULAR response, and 54.4% achieved a moderate EULAR response. However, RDCI was not an independent predictor of remission or EULAR response.

Despite the week association found between comorbidities as assessed by RDCI and response to a first bDMARD, the tool remains important, the authors noted.

“…it is important to consider this simple and useful tool in future prospective and broader studies, since information bias regarding comorbidities may have been responsible for our results,” they concluded.

References

1. Soria Curi Y, Gonzalez Lucero L, Hüttmann FJ, et al. Comorbidities in rheumatoid arthritis: utility of RACI score (Rheumatoid Arthritis Comorbidity Index). Presented at: EULAR 2020; June 3-6, 2020; Abstract FRI0603-HPR. https://ard.bmj.com/content/79/Suppl_1/907.3

2. Garcia S, Fernandes BM, Terroso G, Bernardes M, Costa L. The use of a comorbidity index for predicting clinical response in rheumatoid arthritis patients receiving their first biological agent. Presented at: EULAR 2020; June 3-6, 2020; Abstract FRI0062. https://ard.bmj.com/content/79/Suppl_1/607.1