Computed Tomography Findings as Determinants of Local and Systemic Inflammation Biomarkers in Interstitial Lung Diseases: A Retrospective Cohort Study

Background: Additional to high-resolution computed tomography (HRCT), peripheral blood (PBL) and broncho-alveolar lavage (BAL) could provide biomarkers to distinguish predominantly inflammatory from non-inflammatory/fibrotic interstitial lung disease (ILD) phenotypes. Methods:HRCT of 127 subsequent ILD-board patients were semi-quantitatively evaluated in a standardized way: Reticulation/honeycombing (RET), traction bronchiectasis (TBR) and emphysema (EMP) were classified as non-inflammatory/fibrotic; consolidations (CON), ground glass opacities (GGO), noduli (NDL) and mosaic attenuation (MOS) as active inflammatory findings. These HRCT findings were counted as present or absent in 6 distinct lung regions, resulting scores were graded as minimal (0-1 regions involved), medium (2-4) or extensive (5-6). Associations between routinely assessed PBL/BAL biomarkers with these radiological scores were evaluated using Spearman correlation coefficients; significance of the graded HRCT scores by applying Kruskal-Wallis tests.Results: Blood neutrophil, lymphocyte and eosinophil fraction, neutrophil-lymphocyte ratio (NLR) and BAL lymphocyte fraction consistently showed opposite correlations for inflammatory versus non-inflammatory/fibrotic HRCT finding scores. Blood lymphocyte fraction significantly differed by graded GGO (p=0.032) and CON (p=0.027) extent, eosinophil fraction by TBR (p=0.006) and NLR by CON (p=0.009). C-reactive protein was significantly related to GGO (p=0.023) and CON (p=0.004), BAL lymphocyte fraction to GGO (p=0.017). Conclusions:Blood lymphocyte and eosinophil fraction, NLR, CRP and BAL lymphocyte fraction may aid to differentiate inflammatory from non-inflammatory/fibrotic ILD patterns. Trial registration:This evaluation was based on data from the ILD registry of Kepler University Hospital Linz, as approved by the ethics committee of the federal state of Upper-Austria (EK Nr. I-26-17).