Background: Interstitial lung disease [ILD] is a group of diffuse parenchymal pulmonary disorders which are marked by a high incidence of respiratory failure and mortality when the severity and extent of the condition were unexplored earlier. HRCT, a non-invasive method to comment on the histopathology of the underlying disease has promising diagnostic abilities in staging and assessing the prognosis of the diseases.   
The Aim of the work: To determine the relationship between the HRCT assessed extent and severity scores of interstitial lung disease with functional assessment parameters by standard pulmonary function tests [PFT].
Patients and methods: A hospital-based, cross-sectional study was conducted on 30 patients with clinical suspicion of interstitial lung disease referred from various clinical departments, after excluding those ineligible subjects as per exclusion criteria. ILD scoring was done based on a pre-tested and validated scoring system. The correlation between the morphological HRCT scoring and the functional PFT parameters was evaluated, and the reliability of HRCT scoring was assessed statistically.
Results: Males and females were equally represented in the sample. The mean ILD score was 15.8±5.4 and it did not significantly differ among the males [15.8±5.9] and females [15.7±5.1]. There was a significant negative correlation of total HRCT-ILD scores with Forced vital capacity [FVC] [r=-0.48, p=0.007], Forced expiratory volume in the first second [FeV1] [r=-0.41, p=0.003], Diffusing capacity of the lungs for carbon monoxide [DLCO] [r=- 0.59, p<0.001] and 6-minute walk test [r=-0.38, p=0.004] showing deterioration in functional parameters as the severity score increases.
Conclusion: The study documented the total ILD scores, including the severity and extent of the underlying pathology in HRCT, and established a significant correlation with the functional lung parameters as assessed by PFT.