Background/Purpose: To identify risk of serious infections (SI) according to initial treatment strategy, using conventional synthetic disease modifying anti-rheumatic drugs (csDMARD) and corticosteroids, in patients recruited to the National Early Inflammatory Arthritis Audit.

Methods: An observational cohort study design was used. Population included adults in England with new diagnosis of rheumatoid arthritis (RA), all fulfilling ACR/EULAR 2010 criteria, between April 2018-March 2021. Outcome studied was SI defined by infections requiring hospitalisation (primary admission reason/ nosocomial acquisition) or death (SI stated on death certificate), identified using UK National Health Services (NHS) Digital linkage. Hazard ratios were calculated using single failure Cox proportional hazards models, with confounders adjusted models (age, gender, smoking status, comorbidities, social deprivation) and fully adjusted models included disease factors (seropositivity, 28-joint disease activity score/DAS28). Individuals were considered at risk from date of RA diagnosis and censored at SI event, death, or March 2021 (whichever was earlier).

Results: 20,060 patients with RA were included. Initial DMARD therapy was known for 19,572 patients, of which 11,966 on MTX based strategy, 2789 on csDMARDs combination strategy and 15,319 on corticosteroids. Baseline characteristics categorized by starting (MTX) strategy were: Mean age was 59.6 (+/-15); 62% were female. Smoking status: 20% current; 30% ex-smokers. Comorbidities: 21% hypertension; 9% diabetes; and 10% lung disease. Rheumatoid Factor/CCP antibodies were positive in 69%. At presentation, median scores were 5.1 (interquartile range IQR: 4.3-6.0) for DAS28, 1.1 (IQR: 0.6-1.7) for health assessment questionnaire (HAQ) and 23 (IQR: 16.0-23.0) for musculoskeletal health questionnaire (MSKHQ). There were 519 SI admissions and 17 SI deaths, corresponding to incidence rates per 100 person-years for admissions: 3.19 [95% CI: 2.93-3.48] and deaths: 0.10 [95% CI: 0.06-0.16]. In fully adjusted models, increasing age predicted both SI admissions and deaths. Being a smoker, having comorbidly (i.e diabetes mellitus, lung disease), disease activity, symptom burden measured by MSKHQ and disability by HAQ all associated with SI admission. For each 1 unit increase in DAS28, the risk of SI increased by 8% (hazards ratio HR 1.08 [95% CI:1.01-1.16]). Seropositivity did not associate with SI. Methotrexate based strategies 0.75 [95% CI:0.62-0.91] and csDMARDs combination therapy 0.7 [95% CI:0.53-0.94] were significantly related to lower SI admissions. In unadjusted models, corticosteroid was associated with higher SI admissions 1.29 [95% CI:1.10 -1.62], but in fully adjusted model association was no longer significant. csDMARDs strategies were not significantly associated with SI deaths in any of the models.

Conclusion: Patient and disease factors at diagnosis appear to an important predictor of SI. Infection risk appears to be greatest in those with higher RA disease activity. An important limitation is that NEIAA registry does capture data on treatment changes over time and steroids data beyond baseline.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/serious-infections-hospital-admissions-and-mortality-in-patients-with-early-inflammatory-arthritis-results-from-a-large-uk-cohort/