Age and duration of biological DMARD use are the two significant factors associated with an increased risk of serious infections in RA patients, a WA registry study has shown.
In a ten-year retrospective review of all RA patients treated with bDMARDs in WA, researchers identified 46 hospital admissions for serious infections that warranted antibiotic treatment.
The incidence rate was 9 per 100 person years and the most common infections were skin and soft tissue infections (28%) followed by respiratory infections (26%). Infection rates were highest with infliximab (34.5/100 person years) and lowest for adalimumab (5.3/100 person year).
People who developed serious infections tended to be older age (68 vs 60 years for those with no infection) and had been taking bDMARDs for longer (6.05 years vs 4.68 years for no infection).
No difference in serious infection rates was seen in relation to co-morbidities or glucocorticoid use, but there was not enough information on glucocorticoid exposure in the patients who did not develop infections, the study authors said.
There was also no link between RF or anti-citrullinated peptide (anti-CCP) antibody status on risk of serious infection.
Lead study author Dr Chanakya Sharma of the Department of Rheumatology at Fiona Stanley Hospital, Perth, said the rate of serious infections in the WA study was higher than that seen in a similar but much larger UK registry study covering 19,282 patients (9 vs 5.5/100 person years). However this might be due to the small numbers of patients in the WA registry and results being exaggerated by the influence of ‘outliers,’ he wrote in the Internal Medicine Journal.
The higher rate of serious infections and the link with treatment duration might also be due to relatively high rates of bDMARD switching in the WA cohort, added Dr Sharma.
More than half the patients had been switched from their original bDMARD and the risk of serious infection was known to rise sharply in the first year after starting a new DMARD, the study authors noted.
They concluded that the incidence of serious infection in the WA patients using bDMARDs was on the high end of the range usually reported, but was likely consistent with real world long term use in clinical settings rather than the select groups of patients recruited into clinical trials.
“Based on the findings in this audit, it is recommended that when prescribing bDMARDs, clinicians should consider patient age and duration of bDMARD use when assessing a patient’s risk for serious infection,” they advised.
“Although the contribution of glucocorticoids could not be accurately determined, other studies and our own observations indicate that glucocorticoids are a risk factor for serious infection in RA overall. Accordingly, wherever possible maintenance glucocorticoid use should be minimised to limit toxicity, including the propensity for serious infections,” they added.