Correlation of Lung Texture Analysis by Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) With High-Resolution Computed Tomography and Lung Function in Fibrosing Interstitial Lung Diseases.

Background Progressive pulmonary fibrosis (PPF) is characterized by worsening symptoms, physiological decline (forced vital capacity (FVC) or diffusing capacity for carbon monoxide), and/or radiological progression within a year. It can develop in patients with fibrosing interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF) and other non-IPF ILDs. Confounding variables and intra-individual variability limit the utility of pulmonary function tests. Interobserver variability affects the prognostic value of assessments based on high-resolution CT (HRCT), such as the semi-quantitative Warrick score. This study aimed to evaluate whether quantitative lung texture analysis (LTA) using the Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) software (Mayo Clinic, Rochester, MN) provides an accurate assessment of fibrosis and corresponds with semi-quantitative HRCT scores and functional measures in fibrosing ILDs. Aim To study the correlation between LTA by CALIPER with chest HRCT findings and lung function in fibrosing ILDs. A secondary aim was to determine the utility of LTA by CALIPER in identifying progression in fibrosing ILDs. Methods A total of 57 consecutive patients with fibrosing ILD were included in this hospital-based prospective study conducted in the Department of Pulmonary Medicine, Government Medical College, Kottayam, over a period of 12 months. Patients underwent detailed evaluation, including clinical assessment, semi-quantitative Warrick scoring of HRCT of the chest, FVC by spirometry, six-minute walk test (6MWT), and quantitative LTA obtained from CALIPER at baseline and at six-month follow-up to assess progression. Progression was assessed using changes in HRCT scores, pulmonary function, exercise desaturation, and predefined percentage cut-offs (2%, 5%, 10%, and 20% changes in normal lung percentage by LTA). Data were analyzed using SPSS version 25.0 (IBM Corp., Armonk, NY) with the Spearman correlation test, and associations between CALIPER measures, pulmonary function tests, and HRCT findings were evaluated (p < 0.05 was considered significant). Results Out of 57 patients, 38 (66.7%) were females, with a mean age of 57.84 ± 11.1 years. The most common diagnosis was connective tissue disease-related ILD, followed by idiopathic nonspecific interstitial pneumonia (NSIP). Baseline LTA ground-glass (GG) scores showed a moderate to strong positive correlation with the Warrick alveolitis index (r = 0.675, p < 0.001) and at six months (r = 0.700, p < 0.001). Similarly, LTA fibrosis scores demonstrated significant moderate positive correlations with the Warrick fibrosis index at baseline (r = 0.656, p < 0.001) and at six months (r = 0.631, p < 0.001). Among functional parameters, the strongest correlation was observed between LTA fibrosis score at six months and 6MWT desaturation (r = 0.731, p < 0.001). A 5% reduction in normal lung volume on CALIPER showed diagnostic accuracy of 68.42%, with sensitivity of 51.72% and specificity of 85.71% for predicting disease progression. Conclusions Quantitative LTA using CALIPER demonstrates a strong correlation with semi-quantitative HRCT scoring and a significant correlation with functional indices. CALIPER may serve as a useful adjunct in the routine monitoring of fibrosing ILDs and aid in the early identification of patients at risk for PPF at the earliest.