We aimed to assess the early risk of infection following rituximab in a large national biologics register.
Patients initiating rituximab or standard-of-care (SoC) in the UK-national SLE biologics registry (2010-21) were included. Infection and mortality data were collected from study centres and the Office for National Statistics in the first 12-months. Serious infections included those requiring intravenous antibiotics, hospital admission, or resulting in death. A logistic regression model adjusted for age and sex tested the association of baseline variables with serious infection within the first year.
We included 931 patients; 764 rituximab and 167 SoC (mycophenolate=126, azathioprine=46 and/or cyclophosphamide=38).
At baseline, rituximab patients had a longer disease duration (4 vs 2 years, p=0.04), increased previous immunosuppressant-use (2 vs 1, p<0.0001), more obstructive airways disease (14% vs 7%,p=0.02) and lower maintenance steroid (10mg vs 12.5mg, p<0.0001) and baseline serum IgG (12 vs 15g/L, p=0.024).
In the first year following treatment initiation, there was no difference in the number of serious infections between rituximab and SoC (8% vs 6%,p=0.471), or number of recurrent serious infections (2.5% Vs 1.2%,p=0.309). One rituximab-treated individual died of infection. Commonest infection sites were respiratory (23%), bone/skin (13%) and ENT (10%).
In rituximab-treated patients, cumulative comorbidities (OR 1.34, 95%CI 1.08-1.65), maintenance steroid dose (OR 1.05, 95%CI 1.01-1.08) and hypogammaglobulinaemia (OR 2.3, 95%CI 1.06-5.18) were associated with increased risk of serious infection.
Rituximab-treated SLE patients do not demonstrate an increased risk of serious infections. Baseline hypogammaglobulinaemia, multimorbidity and higher usual oral steroid correlate with infection risk in rituximab-treated patients.