Efficacy of Spirometry and Diffusion Lung Capacity of Carbon monoxide (DLCO) for Predicting of Severity of Interstitial Lung Disease (ILDs) measured by High Resolutions Computed Tomography (HRCT) among Indian Patients

Introduction: High-resolution computed tomography (HRCT) is the preferred method for detecting and monitoring interstitial lung disease (ILD), but its cost, limited access, and radiation risks pose challenges in developing countries. There is a need for affordable, noninvasive, and accessible alternatives to assess ILD severity and prognosis. Objective: The objective of the study is to assess the predictive value of spirometry and diffusion lung capacity of carbon monoxide (DLCO) for detecting the severity of ILD. Methodology: A cross-sectional study conducted among 40 patients with ILD in a tertiary-care hospital in India. The data included age, gender, smoking, HRCT, spirometry, DLCO, 6-min walk test, and medical history. Mann–Whitney U test, Kruskal–Wallis test, and receiver operating characteristic curve were used. Results: The mean age of the participants was 57.18 ± 13.01 years. 62.5% of participants never smoked/consumed tobacco. Fifty percent had severe and 22.5% moderate ILD. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV 1 ), and DLCO declined ( P = <0.001; 0.001; 0.001) with increasing severity of ILD. Sensitivity and 1-Specificity of FVC with cutoff of 79.00 were 0.54 and 0.03, respectively, and with cutoff of 60.50 was 0.72 and 0.41. Sensitivity and 1-Specificity of FEV 1 with cutoff of 75.50 were 0.54 and 0.03, and with cutoff of 60.50 were 0.81 and 0.41. Sensitivity and 1-Specificity of DLCO were 0.90 and 0.03 with cutoff of 56.50. Sensitivity and 1-Specificity of FVC/DLCO were 0.85 and 0.20 with cutoff of 1.43. FVC and DLCO had a high correlation ( P < 0.001). Conclusion: In this study, the DLCO and FVC/DLCO ratio were highly sensitive and specific to predict the severity of ILD independently. Spirometry can also assess the severity of ILD, but it would be better to use it in combination with DLCO.