Rates of serious infections are generally similar for different biologic drugs used in RA, but small differences may be important when selecting therapy for high risk patients, an analysis of UK registry data concludes.

Using etanercept as a reference, the rate of serious infections was slightly lower with certolizumab pegol (hazard ratio 0.75) and slightly higher with tocilizumab (HR 1.21), a review of data from 19,2982 patients found.

Published in the Annals of Rheumatic Diseases, the review by rheumatologists at Guy’s and St Thomas’s NHS Foundation Trust, London, defined serious infections as an infection requiring hospitalisation, IV antibiotics or resulting in death.

The overall rate of serious infections for all biologics was comparable to rates seen in previous registry studies and meta-analyses, at 5.51 cases per 100 patient years.

The 30-day mortality following a serious infection was 10.4% overall, but was higher for sepsis and bacteraemia (45%) and lower for skin infections (2%).

As in previous analyses, respiratory infections were the most common serious infection seen, accounting for 42% of all serious infections, followed by soft tissue and skin infections.

Risk of sepsis was higher with tocilizumab and rituximab (relative risk 1.83 and 2.08 respectively) and lower with infliximab (0.83) compared to etanercept.

The researchers noted that the lower risk of serious infections seen with certolizumab pegol was not apparent in several sensitivity analyses, such as when excluding biologic naïve patients.

They remarked that it would be unusual to see widely different rates of serious infections in biologics acting on similar cellular and cytokine targets, and the new figures contradicted a previous Cochrane review that found four-fold higher rates of serious infections with  certolizumab pegol.

Conversely, “it would be wrong to conclude that certolizumab pegol has a lower rate of serious infections than other biologics,” they added.

“For the majority of patients, biologic therapies remain a safe and efficacious treatment strategy,” they concluded.

For patients whose baseline risk of infection is low, the subtle differences in relative risk of infection mean that the choice of biologic will have very little impact on their subsequent infection risk,” they suggested.

“However, for patients with multiple risk factors who have a high baseline risk of infection, then choosing a drug with a slightly higher relative risk of infection can have a much larger impact on their infection risk

“Recognising the subtleties in the differential infection risk profiles between drugs is a step towards personalised medicine and safer prescribing habits.”