CD4 and pneumonia: Univariate Cox proportional hazard models were used to find risk factors of mortality in HIV/AIDS patients with PCP in derivation cohort; the results indicated significant difference in following variables: age>50years, CD4<50cells/ul, HGB≤90g/L, LDH≤350U/L, hypoalbuminemia, room air PaO2 <70mmHg, breathing rate ≥30 times/min, heart rate ≥130 times/min, later admission to ICU, and some comorbidities, including bacterial pneumonia, CMV pneumonitis, fungal pneumonia, severe pneumonia, and pneumothorax.