Limitations
chronic obstructive pulmonary disease
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
There were several limitations in this study. The sample size in our study was small. Median values were used to fill in the missing data for laboratory examinations and echocardiographic indicators, which may reduce power of test and representativeness. Potential risk factors proposed by other studies such as abnormal estimated glomerular filtration rate, and chronic obstructive pulmonary disease were not considered because of insufficient confirmed cases [