Abstract
Introduction: Interstitial lung diseases comprise diffuse parenchymal diseases of varying radiological patterns and aetiology. They have varying rates of functional progression. Idiopathic pulmonary fibrosis with the Usual interstitial pneumonitis pattern is known to progress in worsening exercise capacity, spirometry and radiology. But ILDs with other radiological patterns like NSIP may also progress in function and radiology. The six-minute walk test is a good indicator of functional exercise capacity. The study assessed the longitudinal changes in the six-minute walk test in different radiological patterns.
Objectives: Primary objective: To assess the radiological pattern and progression of dyspnoea and six-minute walk test over a six-month interval in ILD patients in a tertiary care centre
Study Setting: An Observational longitudinal study in the department of Pulmonary Medicine in Kerala, south India, for one year.
Methodology: Patients diagnosed with ILD within the study period by a multidisciplinary team comprised of pulmonologists and radiologists with more than 20 years of clinical experience based on clinical examination, PFT, and HRCT. A multidisciplinary team assessed radiological patterns. Appropriate investigations were done to identify any underlying auto-immune or connective tissue disorders. The histopathological correlation was obtained wherever possible, and a final diagnosis was obtained. Lung function was assessed by spirometry. The dyspnoea scale was assessed according to the MMRC scale, and a six-minute walk distance was determined. The patients were followed up regularly while on treatment, and the dyspnoea scale and 6MWT were repeated after six months. The association of different radiological patterns and the changes in various parameters in 6MWT was determined.
Results: CTD ILD was the commonest, followed by hypersensitivity pneumonitis and IPF. Longitudinal worsening of the MMRC scale did not have a significant association with any radiologic pattern. The final saturation after 6MWT and 6MWD worsening >25 m in the follow-up test had an association with a UIP pattern on radiology and a diagnosis of IPF. No worsening of 6MWD was observed in COP AND HSP.
Conclusion: A serial six-minute walk test is a good monitoring test to assess exercise capacity for UIP, HSP and OP patterns. The parameters 6MWD and final saturation in 6MWT show predictive associations with radiology.

Key words: Interstitial lung disease, usual interstitial pneumonitis, idiopathic pulmonary fibrosis, six Minute walk test(6MWT), six minute walk distance(6MWD)