In patients suspected of having a pneumonia based on the presence of infiltrates, a persistent (> 24-48 h) PCT level of < 0.1 ??g/L or even 0.1 ??g/L to < 0.25 ??g/L argues against a typical bacterial infection, and physicians should consider sooner rather than later including entities such as pulmonary embolism, acute heart failure, bronchiolitis obliterans organizing pneumonia, Pneumocystisjirov