Computed Tomography Findings as Determinants of Local and Systemic Inflammation Biomarkers in Interstitial Lung Diseases: A Retrospective Registry-Based Descriptive Study

Abstract

Purpose: To evaluate the association of peripheral blood (PBL) and broncho-alveolar lavage (BAL) biomarkers with inflammatory versus fibrotic high-resolution computed tomography (HRCT) findings in interstitial lung disease (ILD) patients.

Methods: HRCT findings of 127 consecutive ILD-board patients were semi-quantitatively evaluated: reticulation/honeycombing (RET), traction bronchiectasis (TBR) and emphysema (EMP) were classified as non-inflammatory/fibrotic; consolidations (CON), ground glass opacities (GGO), parenchymal nodules (NDL) and mosaic attenuation (MOS) as active inflammatory. Each HRCT finding was assessed in six distinct lung regions, resulting scores were graded as minimal (0-1 regions involved), medium (2-4) or extensive (5-6). Associations of routinely assessed PBL/BAL biomarkers with these HRCT scores were evaluated using Spearman correlation coefficients and graphical presentation; significance was tested by applying Kruskal-Wallis tests.

Results: Blood neutrophil, lymphocyte and eosinophil fraction, neutrophil to lymphocyte ratio (NLR) and BAL lymphocyte fraction consistently showed opposite correlations with 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) extent.

Conclusion: 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 Number. I-26-17).

Keywords: Broncho-alveolar lavage; C-reactive protein; Chronic hypersensitivity pneumonitis; Eosinophil; Idiopathic pulmonary fibrosis; Lymphocyte; Peripheral blood.

Fig. 1

Correlation matrix of peripheral blood and broncho-alveolar lavage biomarkers with HRCT finding scores. Values are for Spearman correlation coefficients; colors indicate strength and direction of correlations as shown by the scale on the right side. Bold numbers are for significant correlations, *p < 0.05, **p < 0.01. The line between the EMP and GGO category visually separates non-inflammatory/fibrotic from inflammatory HRCT findings. PBL Peripheral blood, BAL Broncho-alveolar lavage, HRCT High-resolution computed tomography, RET Reticulation/honeycombing, TBR Traction bronchiectasis, EMP Emphysema, GGO Ground glass opacities, CON Consolidations, NDL Parenchymal nodules, MOS Mosaic attenuation, LEU Leukocyte count, NEU Neutrophil fraction, LYM Lymphocyte fraction, NLR Neutrophil to lymphocyte ratio, EOS Eosinophil fraction, CRP C-reactive protein, LDH Lactate dehydrogenase, MAK Macrophage fraction

Fig. 2

Boxplot diagrams of significant findings for PBL biomarkers according to HRCT score categories. Boxplot diagrams depict the median (line), the upper and lower quartile (boxes) and the 95% confidence intervals (whiskers). The red dashed line represents the median of all values. PBL Peripheral blood, LYM Lymphocyte fraction, GGO Ground glass opacities, CON Consolidations, NLR Neutrophil to lymphocyte ratio, EOS Eosinophil fraction, TBR Traction bronchiectasis, CRP C-reactive protein, LDH Lactate dehydrogenase, RET Reticulation/honeycombing, MOS Mosaic attenuation, HRCT High-resolution computed tomography

Fig. 3

Boxplot diagram of BAL lymphocyte fraction according to GGO score categories. Boxplot diagrams depict the median (line), the upper and lower quartile (boxes) and the 95% confidence intervals (whiskers). The red dashed line represents the median of all values. BAL Broncho-alveolar lavage, LYM Lymphocyte fraction, GGO ground glass opacities