Figure 1.

Flow chart of the diagnosis. PCR testing was performed using bronchoalveolar lavage fluid samples from 109 patients. The diagnoses of the 109 patients on discharge included AIP (n=8), AFOP/COP/CEP (n=33), pneumonia (n=24), DILD (n=19), CTD-ILD (n=15), unclassifiable IP (n=4), AHP (n=3), AEP (n=2), and radiation-primed OP (n=1). PCR testing was positive in 60 of the patients, among whom 7 were finally re-diagnosed as having diseases other than viral pneumonia: COP (n=5), radiation-primed OP (n=1), and AEP (n=1). The final diagnosis included viral pneumonia in 53 patients and diseases other than viral pneumonia in 56 patients: unclassifiable IP (n=2); AFOP, COP, or CEP (n=11); radiation-primed OP after breast cancer (n=1); AEP (n=3); AHP (n=3); CTD-ILD [n=12; polymyositis (n=3); dermatomyositis (n=2); amyopathic dermatomyositis with MDA5 antibody (n=2); antisynthetase syndrome (n=5); and rheumatoid arthritis (n=1)], DILD (n=18), and pneumonia due to unknown pathogens (n=4). AEP: acute eosinophilic pneumonia, AFOP: acute fibrinous and organizing pneumonia, AHP: acute hypersensitivity pneumonitis, AIP: acute interstitial pneumonia, CEP: chronic eosinophilic pneumonia, COP: cryptogenic organizing pneumonia, CTD: connective tissue diseases, DILD: drug-induced-ILD, ILD: interstitial lung diseases, IP: interstitial pneumonia, OP: organizing pneumonia, PCR: polymerase chain reaction