Correlation of Spirometry and DLCO with High-resolution Computed Tomography Score in Interstitial Lung Disease Patients

Background and Aim: Interstitial lung disease (ILD) represents a large group of more than 200 different entities and high-resolution computed tomography (HRCT) is the gold standard investigation in diagnosis of ILD. DLCO also serves as the main investigation for monitoring the severity and treatment response in ILD. The aim of our study is to correlate the CT-based visual scoring with spirometry and DLCO of ILD patients. Subjects and Methods: A prospective descriptive study was conducted on 50 patients who were diagnosed to have ILD. Patients were subjected to spiromery, DLCO, and HRCT. HRCT images were analyzed based on CT-based visual scoring, calculated according to lung segments affected on both sides. Finding on each segment was given a score from 1 to 4 as follows: score of (1) for ground-glass opacities, score of (2) for reticulation and fibrotic changes, sore of (3) for bronchiectasis changes, and score of (4) for honeycombing and subpleural cyst. The severity of disease score is calculated as total score maximum of 80 for the whole lung. Pearson’s and Spearman’s correlation coefficient was used for the correlation of pulmonary function test, DLCO scores with CT-based visual scores. Results: A total of 50 ILD patients were included in the study. Results of the Pearson correlation indicated that there is a significant large negative relationship between DLCO and CT score ( r (48) = 0.771, P < 0.001), r = −0.7711, and significant large negative relationship between Spirometry and CT scores, ( r (48) = 0.675, P < 0.001) with r = −0.6748. This negative correlation indicates less the DLCO and Spirometry scores more the lung parenchymal involvement with higher CT score. DLCO’s stronger correlation ( r = −0.771) compared to spirometry ( r = −0.675) suggests that DLCO is a better predictor of lung parenchymal involvement as measured by CT scores. DLCO has more accurate prediction of lung involvement. Conclusion: Visual-based CT scoring offers an advantage over DLCO, where facilities of DLCO are not available. CT-based visual scoring is inversely proportional to DLCO and Spirometry.