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Pneumocystis pneumonia incidence in rheumatic disease dependent upon risk factors

Concomitant steroid-pulse treatment and baseline lymphopenia were among risk factors for pneumocystis pneumonia among a cohort of patients with rheumatic diseases receiving steroid treatment, according to findings published in Arthritis Research & Therapy.

“Incidence of pneumocystis pneumonia in patients with rheumatic diseases remains uncertain,” Jun Won Park, MD, of the division of rheumatology, department of internal medicine at Seoul National University College of Medicine, and colleagues wrote. “Pneumocystis pneumonia is still an important cause of atypical pneumonia in patients without HIV who have immunosuppressed conditions.”

The researchers aimed to investigate pneumocystis pneumonia incidence among patients with rheumatic diseases being treated with 4 or more weeks of non-high-dose steroid therapy. A further aim of the study, which included 28,292 treatment episodes, was to assess the risks and benefits of pneumocystis pneumonia prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX). There were 27,227 patients treated with low-dose steroids, defined as less than 15 mg per day, and 1,065 patients treated with a medium dose — between 15 mg to 30 mg per day — during the 14-year study period.

The primary endpoint was to determine whether the 1-year incidence rate of pneumocystis pneumonia in each dose group was greater than0.1 per 100 person-years.

Results showed that the incidence rate of pneumocystis pneumonia at 1 year was 0.01 per 100 person-years (95% CI, 0.001-0.03) in the low-dose group. Consequently, only the medium-dose group was eligible for further analysis.

Clinicians used TMP-SMX prophylaxis in 45 treatment episodes in the medium-dose group. The rest of the treatment episodes involved no prophylaxis, which the researchers determined to be the control group.

Results of this portion of the study showed that in 1,018 person-years, there were five cases of pneumocystis pneumonia, all among controls (incidence rate = 0.5 per 100 person-years; 95% CI, 0.2-1.2).

Further analysis showed that concomitant steroid-pulse treatment and baseline lymphopenia carried the highest risk for pneumocystis pneumonia. Among 173 treatment episodes that involved one of these risk factors — which the researchers defined as the high-risk group — the incidence rate of pneumocystis pneumonia was 3.4 per 100 person-years (95% CI, 1.1-8). Conversely, there was no pneumocystis pneumonia in other treatment episodes.

TMP-SMX was associated with a reduction in pneumocystis pneumonia risk in the high-risk group, but the finding was not statistically significant (adjusted HR = 0.2; 95% CI, 0.001-2.3).

The incidence rate of adverse drug reactions with TMP-SMX was 41.5 per 100 person-years (95% CI, 22.3-71.6).

The number needed to treat with TMP-SMX to prevent one case of pneumocystis pneumonia among high-risk patients was 31 (95% CI, 17-226), whereas the number needed to treat to cause a serious adverse event was 45 (95% CI, 15-).

“Our results showed the incidence rate of pneumocystis pneumonia in patients with rheumatic disease treated with various steroid dosages, and proposed threshold for steroid treatment in the presence or absence of other risk factors for which primary pneumocystis pneumonia prophylaxis can be justified,” Park and colleagues wrote. – by Rob Volansky

Disclosures: Park reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.