Table 2.

Difference of background factors or duration of corticosteroid administration between patients received low and high dose corticosteroids

Factors	Statistical methods	P-values
Age	Mann-Whitney U test	0.737
Gender	χ2 test	0.200
Disease severity score	χ2 test	0.266
Smoking history	χ2 test	0.594
Dust exposure history	χ2 test	0.916
Dyspnea	χ2 test	0.886
Cough	χ2 test	0.870
Duration	Mann-Whitney U test	0.114

Background data were collected before the start of corticosteroid therapy. Duration was the serial days of corticosteroid administration. “High” and “low” dose of corticosteroids were described as Dosage and duration of corticosteroid therapy in results