However, the NHIRD we used for this study does not contain anti-diabetic medication information in detail. It is difficult to perform the analysis. Nevertheless, this is a good idea for further research. Pneumocystis pneumonia is an emerging infectious disease in immunocompromised hosts such as those with human immunodeficiency virus infection, hematological malignancies, solid tumors, organ transplantations, and connective tissue diseases. During the past 30 years, the worldwide epidemic of HIV dramatically increased the prevalence of PCP, and it is recognized as one of its most common complications. At present, PCP remains an important cause of HIV-associated pneumonia but the incidence of PCP has decreased largely due to highly active antiretroviral therapy and the use of routine prophylaxis against PCP when the CD4 count is, 200 cells/ml. However, the number of patients receiving hematopoietic stem cell and solid organ transplants has increased, and oncologists and rheumatologists have treated patients with progressively more potent immunosuppressive drugs, including high-dose corticosteroids, radiotherapy, tumor necrosis factor-a inhibitors and immunomodulating monoclonal antibodies, which led to an increase in cases of PCP in these populations. The clinical manifestations are quite different between non-HIV infected PCP patients and HIV infected PCP patients, and also vary among patients with different underlying diseases. Research shows that the clinical outcome of NH-PCP is worse than that of HIV-PCP. The mortality of NH-PCP patients ranges from 30 to 60%, compared with 11.3 to 20% in HIV-PCP patients. In addition, in NH-PCP patients who require mechanical ventilation mortality is as high as 60 to 75%. However, few studies have compared the clinical manifestations, treatment and outcome of HIV-PCP and other immunocompromised patients in mainland China.