For the imaging, if patients had interstitial infiltrates or ground glass opacities in the absence of unilobar or multilobar infiltrates, only therapy against “atypical” pathogens (macrolide, quinolone, tetracycline; but not antibiotics for coverage of “typical” bacterial pathogens) was considered appropriate. If both CXR and CT were available, only CT readings were used for further analyses. An infiltrate was required for the diagnosis of pneumonia but no radiography was needed to diagnose a RTI in general.