The aim of the study was to review all cases of Pneumocystis carinii pneumonia (PCP) in patients seen by the Christchurch Hospital Rheumatology service over a 5-year period and to determine the annual incidence of PCP.
The Canterbury Health Laboratory database was searched for rheumatology patients testing positive for PCP from 31 December 2000 to 31 December 2005. The rheumatology database was then searched to identify patients receiving the same immunosuppressant medication as those who developed PCP to determine the annual incidence of PCP in this group.
Four rheumatology patients were diagnosed with PCP during the 5-year period. Two were receiving oral methotrexate (MTX) for rheumatoid arthritis and two were receiving cyclophosphamide (CYC), one each for Wegener's granulomatosis and dermatomyositis. None of the four cases was receiving PCP chemoprophylaxis. Five hundred and forty-seven patients commenced MTX over the same 5-year period and 47 commenced CYC. Only 14 of 47 (29.7%) CYC-treated patients received PCP prophylaxis. The annual incidence of PCP was 0.17% (95% confidence interval (CI) 0.02-0.63) and 5.33% (95%CI 0.65-19.24) in patients prescribed MTX and CYC, respectively. For the 33 patients receiving CYC without concomitant PCP prophylaxis the annual incidence was 9.50% (95%CI 1.15-34.33).
In our study the annual incidence of PCP in patients taking MTX was low and would not support the use of routine PCP chemoprophylaxis. In patients receiving CYC without concomitant PCP chemoprophylaxis the annual incidence of PCP was higher although the number of cases was small. Given the high morbidity and mortality in this group, PCP chemoprophylaxis should be considered.