Objectives To investigate predictors of 10-year risk of revision and 1-year risk of prosthetic joint infection (PJI) and death following total hip/total knee arthroplasty (THA/TKA) in (1) patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (OA); and (2) patients with RA treated with biological disease-modifying antirheumatic drugs (bDMARD) within 90 days preceding surgery compared with non-treated. Methods Register-based cohort study using the Danish National Patient Register, the DANBIO rheumatology register (RA-specific confounders and treatment episodes) and the Danish Hip and Knee Arthroplasty Registers. Survival analyses were used to calculate confounder-adjusted sub-HRs (SHR) and HRs. Results In total, 3913 patients with RA with THA/TKA were compared with 120 499 patients with OA. Patients with RA had decreased risk of revision (SHR 0.71 (0.57–0.89)), but increased risk of PJI (SHR=1.46 (1.13–1.88)) and death (HR=1.25 (1.01–1.55)). In DANBIO, 345 of 1946 patients with RA with THA/TKA had received bDMARD treatment within 90 days preceding surgery. bDMARD-treated patients did not have a statistically significant increased risk of revision (SHR=1.49 (0.65–3.40)), PJI (SHR=1.61 (0.70–3.69)) nor death (HR=0.75 (0.24–2.33)) compared with non-treated. Glucocorticoid exposure (HR=2.87 (1.12–7.34)) and increasing DAS28 (HR=1.49 (1.01–2.20)) were risk factors for mortality. Conclusion Patients with RA had a decreased 10-year risk of revision while the risk of death and PJI was increased compared with patients with OA following THA/TKA. bDMARD exposure was not associated with statistically significant increased risk of neither PJI nor death in this study. Glucocorticoid exposure and increased disease activity were associated with an increased risk of death.

Objectives: To estimate the incidence of COVID-19 hospitalization in patients with inflammatory rheumatic disease (IRD); in patients with RA treated with specific DMARDs; and the incidence of severe COVID-19 infection among hospitalized patients with RA. Methods: A nationwide cohort study from Denmark between 1 March and 12 August 2020. The adjusted incidence of COVID-19 hospitalization was estimated for patients with RA; spondyloarthritis including psoriatic arthritis; connective tissue disease; vasculitides; and non-IRD individuals. Further, the incidence of COVID-19 hospitalization was estimated for patients with RA treated and non-treated with TNF-inhibitors, HCQ or glucocorticoids, respectively. Lastly, the incidence of severe COVID-19 infection (intensive care, acute respiratory distress syndrome or death) among hospital-admitted patients was estimated for RA and non-IRD sp - individudals. Results: Patients with IRD (n = 58 052) had an increased partially adjusted incidence of hospitalization with COVID-19 compared with the 4.5 million people in the general population [hazard ratio (HR) 1.46, 95% CI: 1.15, 1.86] with strongest associations for patients with RA (n = 29 440, HR 1.72, 95% CI: 1.29, 2.30) and vasculitides (n = 4072, HR 1.82, 95% CI: 0.91, 3.64). There was no increased incidence of COVID-19 hospitalization associated with TNF-inhibitor, HCQ nor glucocorticoid use. COVID-19 admitted patients with RA had a HR of 1.43 (95% CI: 0.80, 2.53) for a severe outcome. Conclusion: Patients with IRD were more likely to be admitted with COVID-19 than the general population, and COVID-19 admitted patients with RA could be at higher risk of a severe outcome. Treatment with specific DMARDs did not affect the risk of hospitalization.

Background Lymphomas comprise a heterogeneous group of malignant diseases with highly variable prognosis. Rheumatoid arthritis (RA) is associated with a twofold increased risk of both Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphoma (NHL). It is unknown whether treatment with biologic disease-modifying antirheumatic drugs (bDMARDs) affect the risk of specific lymphoma subtypes. Methods Patients never exposed to (bionaïve) or ever treated with bDMARDs from 12 European biologic registers were followed prospectively for the occurrence of first ever histologically confirmed lymphoma. Patients were considered exposed to a bDMARD after having received the first dose. Lymphomas were attributed to the most recently received bDMARD. Results Among 124 997 patients (mean age 59 years; 73.7% female), 533 lymphomas were reported. Of these, 9.5% were HL, 83.8% B-cell NHL and 6.8% T-cell NHL. No cases of hepatosplenic T-cell lymphoma were observed. Diffuse large B-cell lymphoma (DLBCL) was the most frequent B-cell NHL subtype (55.8% of all B-cell NHLs). The subtype distributions were similar between bionaïve patients and those treated with tumour necrosis factor inhibitors (TNFi). For other bDMARDs, the numbers of cases were too small to draw any conclusions. Patients with RA developed more DLBCLs and less chronic lymphocytic leukaemia compared with the general population. Conclusion This large collaborative analysis of European registries has successfully collated subtype information on 533 lymphomas. While the subtype distribution differs between RA and the general population, there was no evidence of any modification of the distribution of lymphoma subtypes in patients with RA treated with TNFi compared with bionaïve patients.

We aimed to investigate gender differences in disease manifestations, patient-reported outcomes, comorbidities and treatment effectiveness among patients with PsA treated with their first TNFα inhibitor (TNFI). In this observational cohort study, the DANBIO register provided prospectively collected data on PsA patients who initiated their first TNFI in 2000–15. Comorbidity information was achieved from the Danish Nationwide Patient Register. Response to treatment was assessed according to EULAR and ACR criteria at 3 and 6 months. Cox and logistic regression models analysed the impact of gender on TNFI persistence and response, respectively, while adjusting for a priori selected confounders including clinical-, laboratory- and patient-reported factors, comorbidities and lifestyle characteristics. A total of 1750 PsA patients (935 women) were included. At baseline, women were older (49 years/47 years), more often smokers (32%/26%), had worse patient-reported scores (e.g. global score 71 mm/65 mm) and higher frequencies of hospital-diagnosed anxiety or depression (7%/4%) and chronic pulmonary disease (7%/3%) than men (all P < 0.01). Median TNFI persistence was 3.8 years (95% CI: 3.0, 5.7) in men vs 1.4 (1.1, 1.8) in women (P < 0.001). Men had higher odds of achieving response after 3 and 6 months, for example, adjusted odds ratio = 3.2 (1.6, 6.1) for EULAR good/moderate response (vs women) at 6 months. Male gender was strongly associated with greater TNFI treatment effectiveness. Adjustment for baseline risk factors including patient-reported outcomes, disease activity, comorbidities and lifestyle factors did not influence this relationship, which suggests a role of biological factors.

Objectives: MTX is the most commonly recommended DMARD for first-line treatment of RA, however, it has been hypothesized to cause lung disease as an adverse effect. We investigated the risk of interstitial lung disease (ILD) and acute and chronic respiratory failure in persons with RA treated with MTX and other medications. Methods: From the Danish National Patient Register (NPR) and the DANBIO register for rheumatic diseases, we retrieved data on 30 512 persons with RA registered in 1997–2015. Information on ILD and respiratory failure was obtained from the NPR. Information on age and sex for all Danish citizens was obtained from the Danish Civil Registration System. MTX and other medication purchases were retrieved from the Danish Prescription Registry. Associations between MTX and lung disease outcomes were analysed in Cox regression models with adjustment for age, calendar time, sex and other medications. Standardized incidence ratios (SIRs) of lung disease were calculated to compare the RA population with the general population. Results: There was no increased risk of lung disease with MTX treatment [one or more purchases compared with no purchases; HR 1.00 (95% CI 0.78, 1.27) for ILD and 0.54 (95% CI 0.43, 0.67) for respiratory failure] at the 5 year follow-up. The SIR was three to four times higher for ILD in MTX-treated persons with RA, but similar to the whole RA population compared with the background population. Conclusion: Persons with RA had an increased risk of ILD compared with the general population, but there was no further increased risk associated with MTX treatment.

Objective: To investigate temporal trends in the incidence and prevalence of gout in the adult Danish population. Methods: Using the nationwide Danish National Patient Registry, we calculated the number of incident gout patients (per 100 000 person-years) within each 1 year period from 1995 to 2015 and the prevalence of gout in 2000 and 2015. Further, we calculated age- and gender-specific incidence rates of gout from 1995 to 2015. Results: We identified a total of 45 685 incident gout patients (72.9% males) with a mean age of 65 years (s.d. 16) at diagnosis. In both genders, an increase in age-standardized incidence rates was observed from 32.3/100 000 (95% CI 30.7, 33.9) in 1995 to 57.5/100 000 (95% CI 55.6, 59.5) in 2015 (P < 0.001). Similar trends were observed for 8950 cases diagnosed in rheumatology departments. We likewise observed an increase in the prevalence of gout from 0.29% (95% CI 0.29, 0.30) in 2000 to 0.68% (95% CI 0.68, 0.69) in 2015. Conclusions: The annual incidence rate of gout increased by almost 80% in Denmark between 1995 and 2015. The prevalence increased by nearly 130% between 2000 and 2015. Reasons for this are unknown but may include an increase in risk factors (e.g. obesity, diabetes mellitus), longer life expectancy and increased awareness of the disease among patients and/or health professionals.