medwireNews: Individuals with rheumatoid arthritis (RA) have a significantly higher risk for serious infections while receiving tumor necrosis factor (TNF) inhibitor therapy than those with psoriatic arthritis (PsA), Norwegian researchers report.
“Although the results need to be interpreted with caution given the many important differences between the RA and PsA population, our findings indicate that the clinician should consider the rheumatological diagnoses when assessing the risk of future [serious infection] in patients starting a TNF [inhibitor],” say Ingrid Egeland Christensen (Diakonhjemmet Hospital, Oslo) and co-investigators.
Their study included 2359 patients with RA (n=1352) or PsA (n=1007) from the NOR-DMARD registry who initiated TNF inhibitor treatment between 2009 and 2018. During this time, there were 1778 treatment courses initiated among the individuals with RA and 1391 initiated among those with PsA.
At baseline, patients with RA were significantly older than those with PsA (mean 53.2 vs 48.2 years), were more likely to be women (75.4 vs 57.3%), had a longer median disease duration (6.9 vs 5.2 years), higher mean DAS28-CRP scores (4.0 vs 3.5), higher rates of chronic obstructive pulmonary disease or asthma (10.1 vs 6.7%), and were more likely to be using methotrexate (73.2 vs 59.1%) and prednisolone (56.5 vs 29.6%).
Using data from the Norwegian Patient Registry and the Norwegian Cause of Death Registry, the researchers established that, during the study period, there were 187 serious infections, defined as an infection requiring hospital admission with at least a one-night stay and/or an infection causing death. The most common infection type was of the respiratory tract (37%).
Christensen et al report in the Annals of the Rheumatic Diseases that the incidence of serious infections was higher in the people with RA relative to those with PsA, at 4.17 versus 2.16 cases per 100 patient–years.
Furthermore, Cox regression analysis, adjusted for age and sex, revealed that the people with PsA had a significant 41% lower risk for serious infection than those with RA. This risk difference was only marginally attenuated – to 35% – after adjustment for further differences in baseline characteristics.
“However, the additive effect of multiple risk factors in the RA population, including more frequent prednisolone use, may explain some of the increased risk of [serious infections] in patients with RA,” Christensen and co-authors write.
“Another explanation could be the RA disease itself, through disease-related alterations in host defence,” they add.
The team concludes: “Recognising the elevated risk in patients with RA supports the heightened awareness of [serious infections] during follow-up of these patients.”
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