The serious infection risk associated with rituximab treatment for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is high but can be offset by co-prescribing co-trimoxazole, data from a single-center, retrospective study reaffirm.
Over the course of a 3-year study period, 14 (28%) of 50 patients with AAV treated with rituximab experienced at latest one severe infection defined as a grade 3 or higher event. The incidence of severe infections was 15.4 per 100 person-years.
However, a lower rate of infections was seen in patients who had been co-prescribed co-trimoxazole (trimethoprim and sulfamethoxazole), Francesco Dernie, a fifth-year medical student at the University of Oxford (England), reported at the British Society for Rheumatology annual conference.
“In the case of rituximab, the depletion of B cells and associated immune suppression is a double-edged sword, allowing effective disease control, but also leaving the body vulnerable to opportunistic and severe infections,” Dernie said at the meeting.
Of the patients who developed a severe infection on rituximab, just 7% had been treated with co-trimoxazole. In comparison, 44% of those who did not get a severe infection had received co-trimoxazole. Multivariate analysis confirmed that co-trimoxazole use was an influencing factor, with an odds ratio (OR) of 0.096 (95% confidence interval, 0.009–0.996; P = .05).
Another finding was that patients with low immunoglobulin G levels (less than 6 g/L) were more likely to develop a severe infection than were those with higher IgG levels. Indeed, the OR for hypogammaglobulinemia and the risk for infection was 8.782 (95% CI, 1.19–64.6; P = .033).
“Our results support the monitoring of IgG levels to identify patients who may be more susceptible to infection, as well as the prescription of prophylactic co-trimoxazole to reduce overall severe infection risk,” Dernie and associates concluded in their abstract.
It’s a “really important message around co-trimoxazole,” observed Neil Basu, MBChB, a clinical senior lecturer and honorary consultant at the Institute of Infection, Immunity & Inflammation, University of Glasgow (Scotland).
“It still frustrates me when I see that patients haven’t received that while receiving rituximab. Of course, co-trimoxazole can have its problems,” said Basu, who was not involved in the study. “It’s not uncommon for patients to develop reactions or be intolerant to the drug.”
Raashid Luqmani, DM, a senior coauthor of the work and professor of rheumatology at the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Science, University of Oxford, said: “The tolerance of co-trimoxazole has been remarkably good in this cohort.” If there was a problem with using co-trimoxazole, then “our standard would be to go with trimethoprim alone as the next in line and follow that with inhaled pentamidine. So, it’s kind of following what we would all generally do,” Luqmani said.
These data add further support for coprescribing antibiotic treatment with rituximab, he suggested.
“Worry about infection, worry about it a lot; not just worry about it, do something about it,” Luqmani said, and co-trimoxazole “is probably an effective means to do something about it.”
To look at the characteristics of and risk factors for serious infections associated with rituximab use in AAV, Dernie and associates retrospectively examined the electronic records of patients who had been treated between August 2016 and August 2019. Follow-up was until August 2020.
Of the 50 patients identified, nearly half (48%) were men. The average age was 60 years, ranging from 25 to 90 years. Most (n = 36; 72%) patients had a diagnosis of granulomatosis with polyangiitis, while another 2 (4%) had microscopic polyangiitis, 1 (2%) had eosinophilic granulomatosis with polyangiitis, and 11 (22%) had an overlapping type of vasculitis or undefined AAV.
Of the 18 severe infection events recorded, most (56%) involved the respiratory tract. Less than one-third (28%) were sepsis or neutropenic sepsis events, and there was one case each (6%) of cellulitis, complicated urinary tract infection, and recurrent wound infection.
There were “small numbers of individual comorbidities that were not sufficient to enter into our regression analysis,” Dernie noted. “It’s likely that comorbid conditions such as COPD [chronic obstructive pulmonary disease] also contribute to an individual’s risk of developing severe infections, and thus should factor into their individualized management.”
Dernie acknowledged in discussion: “One of the limitations of the study was we just looked at patients in a time when they were receiving rituximab, so they may have historically been exposed to other treatment options.” However, he added, “they weren’t having any other major DMARDs or immunosuppressive treatments at the time.”
Luqmani observed: “If you look at Francesco’s data on the hypogammaglobulinemia at the start of rituximab, that probably gives you a good idea of just how immunosuppressed these patients were already before we got to this point.”
Luqmani added: “I suspect that’s in keeping with a lot of other centers that have started using rituximab an awful lot for patients who previously had episodes of vasculitis treated with other disease-modifying therapies, particularly cyclophosphamide.”
But for how long should co-trimoxazole be given after the last rituximab dose? asked the chair of the session, Richard Watts, DM, of Norwich (England) Medical School. These data are purely observational, so it’s not possible to say, Dernie noted: “The patients that we included as having co-trimoxazole seem to be on it more or less consistently, permanently,” he said.
What about the best dose? “It’s a tricky one,” Luqmani said, as “we not only use co-trimoxazole for prophylaxis, but we often also want to use it for treatment of the vasculitis itself.”
It’s very likely that there was a mix of patients in the analysis that had received co-trimoxazole as either a treatment or prophylaxis, which means different doses, he said.
“It might be interesting to know whether there was a difference” between doses used and the prevention of infection, added Luqmani, “but I suspect the numbers are too small to tell.”
Dernie, Luqmani, and the other coauthors had no disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.