High Biologic Blood Levels Increases the Risk of Infections in RA Save

A big concern of most is the risk of infection with use of tumour necrosis factor inhibitor (TNFi) and biologic drugs.  While studied in both trials and in post-marketing studies, it is unknown if infection risk is dose-dependent.

In abstract OP0229 UK researchers have shown high biologic blood levels are associates with an increased risk of total infections in RA, but not serious infetions.

They merged data from two large British RA registries (British Society for Rheumatology Biologics Register-RA [safety data] and the Biologics in RA Genetics and Genomics Syndicate [serological samples]) to assess the effect of biologic drug levels in rheumatoid arthritis (RA) patients on all infections (AI) and SI (infections requiring hospitalisation, IV antibiotics or lead to death.

Serum samples and drug levels were measured at 3, 6,  and 12 months after biologic initiation and the risk of first and total infections within the first year was analysed.

The RA population (n=703) of predominantly female patients on biologics  - 286 etanercept, 179 adalimumab, 120 certolizumab, 104 tocilizumab and 14 infliximab were studied. The majority of enrolled patients were on their first biologic (89%). The adjusted hazard ratio for AI within  the first year differed significantly between the two groups with the HL group having a 50 percent higher risk of all infections (HR: 1.51; 95% CI: 1.14, 2.01).

The most common types of AI in the HL group were lower (34%) and upper (16%) respiratory tract infections, urinary tract infections (15%), skin infections including shingles (8%).

Serious inffections, however, were not increased with high vs. low doses of biologic exposure. 

This study suggests that monitoring drug levels may be helpful in prediction of infectious complications in RA patients.

Biologic dose tapering in patients with high biologic levels who were able to achieve stable remission may lower infection risk.