Provided are a method for detecting respiratory tract infectious diseases associated with bacterial infection, a method for selecting respiratory tract infectious disease patients for administration of an antibiotic, and a method for determining the timing for ending administration of the antibiotic to respiratory tract infectious disease patients to whom the antibiotic is being administered, said methods being characterized by appropriately selecting respiratory tract infectious disease patients to whom the antibiotic should be administered, by being capable of optimizing the administration period of the antibiotic, by being capable of treating a respiratory tract infectious disease associated with bacterial infection, and by using a measured value for blood-borne sCD14-ST as an indicator.
