Yukawa K, et al. - In this retrospective cohort study, researchers clarified the risk factors for Pneumocystis jirovecii pneumonia (PCP) in patients with rheumatoid arthritis (RA), and established indications for administering trimethoprim in combination with sulfamethoxazole (TMP/SMX). They analyzed data from 2,640 patients (2010–2014) in whom RA was diagnosed but had not received a prophylactic administration of TMP/SMX. Clinical parameters were compared between patients with PCP (n=19) and those without (n=2,621) to evaluate risk factors. Using a scoring system based on odds ratios calculated for parameters (eg, older age, higher doses of prednisolone and methotrexate, and a greater number of immunosuppressant medications), PCP risk was determined. Finding suggested that prophylactic administration of TMP/SMX for PCP should be considered for patients with RA who score ≥ 5 points with this system.