Immunosuppressant medications (ISPs) increase the occurrence of Pneumocystis jirovecii pneumonia (PCP) in rheumatoid arthritis (RA) patients. The prophylactic administration of trimethoprim/sulfamethoxazole (TMP/SMX) for PCP is effective but has serious adverse effects and so should be selectively used for patients at high risk. The aims of this study were to clarify the risk factors for PCP in RA patients and to establish the indications for administering TMP/SMX.
This retrospective cohort study analyzed data from 2640 patients (2010-2014) diagnosed as having RA who had not received a prophylactic administration of TMP/SMX. The risk factors for PCP were evaluated by comparing the clinical parameters between patients with PCP (PCP group, n = 19) and those without (non-PCP group, n = 2621).
The PCP group was older (70 vs. 64 years), received higher doses of prednisolone (6.2 vs. 2.4 mg/d) and methotrexate (7.7 vs. 5.2 mg/wk), and had a greater number of ISPs (1.3 vs. 0.8) (p < 0.05). We stratified the PCP risk using a scoring system based on odds ratios (ORs) calculated for these parameters (methotrexate ≥6 mg/wk OR = 4.5, 1 point; age ≥65 years, OR = 3.7, 1 point; ≥2 ISPs, OR = 3.7, 1 point; prednisolone ≥5 mg/d, OR = 12.4, 3 points). The incidence of PCP among patients scoring 0 to 2 points was 0.04%; 3 to 4 points, 2.3%; and 5 points or more, 5.8%.
The prophylactic administration of TMP/SMX for PCP is recommended for RA patients who score at least 5 points with our system.