Compared with the general population, patients with systemic lupus erythematosus (SLE) have a higher risk for Pneumocystis jirovecii (P jirovecii; formerly P carinii) pneumonia (PCP) infection, with risk factors including the male sex, use of intravenous (IV) steroid pulse therapy, oral steroid dosing of greater than 7.5 mg/day, use of mycofenolate mofetil (MMF), and end-stage kidney disease (ESKD), according to study results published in Arthritis Care & Research (Hoboken).
In a nationwide retrospective cohort study conducted in Taiwan, the researchers sought to assess the risk for PCP infection among patients with SLE from the National Health Insurance (NHI) program, a single-payer health care system that provides comprehensive health care for more than 99% of Taiwanese residents. Under the NHI program, patients with certain severe diseases, including SLE, are enrolled in the Registry of Catastrophic Illnesses. The current analysis was conducted between January 1, 1997, and December 31, 2012. Non-SLE control participants were chosen from the 2000 Longitudinal Health Insurance Database.
Incidence rates (IRs) of PCP infection were compared between 24,367 patients with SLE and 243,670 age- and sex-matched non-SLE control participants. Mean age of the participants was 35.94 years; 88.7% of the participants were women. The median duration of follow-up was 8.58 years and 12.07 years in the SLE and control groups, respectively.
Overall, PCP infections were reported in 55 patients with SLE and 28 control participants. Despite the shorter duration of follow-up in the SLE group, the PCP infection rate was significantly higher than in the control group (0.23% vs 0.01%, respectively; P <.001). According to Kaplan-Meier analysis, a significantly higher risk for PCP infection was also reported in the SLE cohort than in the matched control cohort (log-rank P <.001).
The overall IR of PCP infection in the SLE was 2.63 per 10,000 person-years, with a significant IR ratio of 27.65 (95% CI, 17.2-45.3: P <.001). Further, in the SLE group, IRs were higher among men in each age stratum. Among patients of both sexes in the SLE group, IRs differed according to age subgroup, with those aged younger than 18 years exhibiting the highest IR and followed by those aged greater than 50 years. In contrast, IRs increased with age among participants in the control cohort.
In the SLE cohort, male sex (hazard ratio [HR], 2.42; 95% CI, 1.31-4.46; P <.01), recent use of MMF (HR, 4.43; 95% CI, 2.17-9.04; P <.001), IV steroid pulse treatment (HR, 108.73; 95% CI, 38.16-309.86; P <.001), oral steroid dose greater than 7.5 mg/day (HR, 4.83: 95% CI, 3.11-11.04 mg/d; P <.001), and presence of ESKD (HR, 1.74; 95% CI, 1.00-3.00; P =.01) were all associated with the development of PCP infection. However, use of hydroxychloroquine reduced the risk for PCP in the SLE group (HR, 0.51; 95% CI, 0.29-0.88; P =.01). According to the multivariate Cox proportional hazard model, the use of cyclophosphamide was not associated with PCP infection.
A major limitation of the current study was its retrospective design and claims-based dataset, with the unavailability of information such as personal history, clinical manifestations of the disease, and test results.
Researchers concluded, “…these risk factors might be the foundation of an elective [PCP] prophylaxis guideline in SLE care.”
Wang W-H, Lai C-C, Huang Y-F, et al. Pneumocystis jirovecii pneumonia in systemic lupus erythematosus: a nationwide cohort study in Taiwan. Arthritis Care Res (Hoboken). Published online February 28, 2021. doi:10.1002/acr.24584