ABSTRACT
Background: Infiximab is usually given every 8 weeks. To increase dosage, the dose can be increased or the interval between infusions shortened. To minimize patient visits and workload for the medical staff during the Corona pandemic, we intended to change all infiximab infusions to 8 week intervals. For patients with infammatory bowel disease, a trough level of serum (s-) concentration of infixi-mab of 3-7 μ g/ml is recommended. In Rheumatology the usefulness of assessing s-concentration is controversial. (1, 2) Objectives: To evaluate if 8 week interval infiximab dosage, with retained weekly dose, can be used in arthritis patients, without worsening of disease activity or general health and study if s-concentration of infiximab is related to disease activity and general health. Methods: All arthritis patients on stable infiximab treatment were evaluated at the time for infiximab infusion. Disease activity, DAS28-CRP, VAS pain, global, fatigue, doctors' global, HAQ, and ASDAS-CRP, BASFI for spondyloarthritis (SpA) patients were registered in the Swedish Rheumatology Quality registry (SRQ). Blood tests for CRP, ESR and s-concentration of infiximab were taken before infusion start. S-concentration was analysed at Karolinska Hospital, Solna, Sweden with an in-house ELISA. Antibodies were assessed if s-concentration was <0.5 μ g/ml. Patients with infusion intervals less than 8 weeks were recommended a switch to 8 week intervals with maintained weekly dose of infiximab. The new dose was given the same day and patients with changed doses were re-evaluated after 24 weeks. Paired samples T-test and Wilcoxon signed rank test for paired data were used for comparison of disease activity and general health after dosage change. Linear regression analyses were used to explore associations between s-concentration, disease activity and general health. Results: Of 91 assessed patients, 66 with shorter intervals were recommended dosage change. The remaining 25 patients had infiximab every 8 weeks and served as controls. For baseline characteristics see Table 1. Dosage was changed in 58 patients and 90% (n=52) remained on 8 week intervals after 24 weeks, with a mean (SD) dose of infiximab of 5.3 (1.9) mg/kg. All assessed disease variables (DAS28-CRP, VAS pain, global, fatigue, Dr global, HAQ, ASDAS-CRP, BASFI, CRP and ESR) remained unchanged (p=0.051 (pain)-0.83) (Figure 1 A, B) while S-concentration was lower (p<0.001) at follow up. S-concentration of infiximab did not relate to disease activity neither at baseline nor at follow up (p=0.15-0.24). (Figure 1 C, D) Conclusion: Adjustment of infiximab dosage to every 8 weeks worked for a majority of the arthritis patients in this clinical setting without worsening of disease activity or general health. S-concentration of infiximab did not relate to disease activity or general health.
ABSTRACT
Background: Studies from COVID-19 case-repositories among patients with rheumatic diseases have assessed associations (relative risks) between characteristics of the disease and adverse COVID-19 outcomes. Such designs are susceptible to bias from selection of cases reported. Few studies have assessed absolute and relative risks for COVID-19 outcomes in population-based cohorts of patients with inflammatory joint diseases, nor compared these risks to those in the general population. Objectives: To estimate all-cause mortality, absolute and relative risks for severe COVID-19 in patients with chronic inflammatory joint diseases, compared over time and to the general population. Methods: We updated a multi-register nationwide linkage (“ARTIS”) on adults with RA, PsA, AS, SpA or JIA and population referents (matched on sex, age, and region), with data on hospitalizations, admission to intensive care (ICU), and deaths due to COVID-19. We calculated all-cause mortality March-September 2015-2020, and absolute and relative risks for COVID-19 outcomes March-September 2020. Patients were compared to population referents using hazard ratios (HR) from Cox models adjusted for comorbidities and socio-economy. Results: We identified 110567 individuals with inflammatory joint disease (53455 with RA) in Sweden on March 1st 2020, and 484277 matched general population subjects. In all cohorts, the absolute risk of death from any cause in 2020 was higher than 2015-2019 (Figure 1), with a peak in mid-April, but the relative risks of death (vs. the general population) 2020 remained similar to HRs for 2015-2019 (HR for 2020 in Table 1). Among all individuals with inflammatory joint disease in 2020, the risk for hospitalization, admission to ICU, and death due to COVID-19 was 0.5%, 0.04% and 0.1%, respectively (Table 1). HRs (vs. the general population) were elevated for almost all outcomes. HRs for COVID-19 related outcomes (Table 1) were higher than for non-COVID-19 outcomes;adjustment for co-morbidities and socio-economy explained much of these increases, somewhat less so for the former. Conclusion: Risks of severe COVID-19 were increased among patients with inflammatory joint diseases, but similar increases were seen for non-COVID-19 morbidity. Co-morbidities and socio-economy explain much of this increase.