Risk Score Predictive of Serious Infections in Patients With Rheumatoid Arthritis

pneumonia, lungs
Researchers identified risk factors for serious infections in rheumatoid arthritis and validated the RABBIT risk score in real-life settings.

In patients with rheumatoid arthritis (RA), longer disease duration, history of previous serious infections (SIs), comorbidities, and high glucocorticoid dose were found to be independent predictors of the development of SIs, according to study results published in Rheumatology (Oxford).

Researchers sought to identify risk factors for SIs in patients with RA and validate the use of the RA Observation of Biologic Therapy (RABBIT) risk score in real-life settings.

A multicenter, prospective, cohort study was conducted by the RA Study Group of the Greek Rheumatology Society. Study inclusion criteria were individuals aged at least 18 years with an RA diagnosis based on the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria. Data on patient demographics, disease characteristics, treatment patterns, and comorbidities were documented at first assessment and at 1 year.

Of 2491 participants who were initially evaluated, a total of 1557 patients (62.5%) with RA were re-evaluated approximately 1 year later and included in the current study. During 1663 patient-years of follow-up, 38 infections were reported among 35 patients (incident rate ratio [IRR], 2.3 per 100 patient-years). The most common infections were respiratory tract infections (50%), herpes zoster infection (13%), pyelonephritis (11%), and acute bacterial skin and skin structure infections (11%).

Patients who developed SIs had a longer disease duration, higher Health Assessment Questionnaire score at first evaluation, and were more likely to have a history of previous SIs, cardiovascular disease, chronic lung disease, and chronic kidney disease. According to multivariate analysis, longer disease duration (IRR, 1.05; 95% CI, 1.003-1.10; P =.018), history of previous SIs (IRR, 4.15; 95% CI, 1.70-10.12; P =.002), chronic lung disease (IRR, 3.13; 95% CI, 1.35-7.27; P =.008), diabetes (IRR, 2.55; 95% CI, 1.06-6.14; P =.036), and daily prednisolone dose of 10 mg or greater (IRR, 4.77; 95% CI, 1.47-15.5; P =.009) were all independent risk factors for SIs.

Using the RABBIT risk score in 1359 participants, the expected SI incidence rate was 1.71 per 100 patient-years, which did not significantly differ from the observed rate of 1.91 per 100 patient-years (P =.97).

Study limitations included the 37.5% of patients who were lost to follow-up, the lack of data on some SIs, including herpes zoster, which were managed by other specialists, and the inclusion of patients with only long-standing disease who were enrolled in tertiary referral centers.

Researchers concluded that the use of the RABBIT score was an accurate, well-balanced predictor of risk for infection in the RA patient cohort. Disease characteristics, comorbidities, and glucocorticoids, rather than biologic disease-modifying antirheumatic drugs, were all associated with the development of SIs.

In patients with RA who were identified as being at high risk for SIs, application of preventive measures, including reducing glucocorticoid exposure; implementing universal vaccination coverage for influenza, pneumococcus, and herpes zoster; and promoting awareness among rheumatologists and patients for recognizing early signs of infection, can help to further reduce this risk.


Thomas K, Lazarini A, Kaltsonoudis E, et al. Incidence, risk factors and validation of the RABBIT score for serious infections in a cohort of 1557 patients with rheumatoid arthritis. Rheumatology (Oxford). Published online December 9, 2020. doi:10.1093/rheumatology/keaa557