Background and Aims: Ununified CT protocols of the multicenter may lower the accuracy of the emphysema extent in the multicenter studies. Therefore, after standardizing various CT protocols through the kernel conversion technique, we aimed to investigate the correlation between the quantitative extent of emphysema and the prognosis of COPD cohort patients.

Methods: CT scans of the KOCOSS cohort reconstructed with a sharp kernel were converted to a smooth kernel using the commercially available software (A-view COPD, Coreline, Seoul, KR), and the percentage of the low-attenuation area below -950HU (%LAA-950) in the whole lung was defined as emphysema extent. Both converted and unconverted %LAA-950 were checked with the correlation with various outcomes of COPD. 

Results: Of 484 COPD patients, most are male (n=444, 91.7%), and the average age was 67.7±8.1 years. In addition, 417 (86.2%) experienced smoking exposure, and 314 (64.9%) were still smokers. Compared with unconverted CT scans, after kernel conversion, %LAA-950 showed a higher correlation with FEV1 (r=-0.412, p<0.001), DLCO (r=-0.415, p<0.001), RV/TLC (r=0.420, p<0.001), mMRC (r=0.252, p<0.001), SGRQ-c (r=0.212, p<0.001) than the original version.In multivariable logistic regression, DLCO (?=-0.215, p<0.001) and %LAA-950 in converted CT (?=0.207, p=0.011) were significant factors associated with the quality of life in COPD patients.

Conclusions: %LAA-950 after CT protocol standardization significantly improved its correlation with lung function and clinical parameters in COPD patients enrolled from multicenter using different CT protocols.