Background: To investigate the effect of modern immunosuppression on the incidence, risk factors, morbidity, and mortality of Pneumocystis pneumonia (PCP) in recipients of kidney transplants.
Methods: We conducted a retrospective cohort study of 32,757 Medicare primary transplant recipients in the United States Renal Data System from January 1, 2000 through July 31, 2004. PCP infection was defined by Medicare claims using International Classification of Disease, 9th Revision codes. The incidence of PCP infections, graft loss, and death were measured.
Results: There were a total of 142 cases (cumulative incidence 0.4%) of PCP after kidney transplantation during the study period. By using multivariate analysis with Cox regression, expanded criteria donor, donation after cardiac death, and earlier year of transplant were associated with development of PCP disease. Induction immunosuppression and acute rejections were not associated with risk for PCP infections. However, based on adjusted hazard ratio (AHR), maintenance immunosuppression regimens containing the combination of tacrolimus and sirolimus (AHR 3.60, confidence interval [CI] 2.03-6.39), Neoral and mycophenolate mofetil (AHR 2.09, CI 1.31-3.31), and sirolimus and mycophenolate mofetil (AHR 2.77, CI 1.40-5.47), were associated with development of PCP. As a time dependent variable, PCP was associated with an increased risk of both graft loss and death.
Conclusion: PCP infections are rare in the modern era of prophylaxis; however, these infections are a serious risk factor for graft loss and patient death, in particular, in patients who are on sirolimus as part of the immunosuppressive regimen. The median time to development of PCP after transplant was 0.80+/-0.95 years, suggesting a longer period of PCP prophylaxis.