Table 1.

Biomarkers involved in exudative and fibroproliferative phases of ARDS

Pathophysiological features of ARDS	Biomarker/source of biomarker
Exudative phase of ARDS (days 0–7)
A. Lung injury
1.Epithelium damage (i) Alveolar epithelial type 1 cells (ii) Alveolar epithelial type 2 cells (iii) Clara cells	RAGE, HTI56 Surfactant (SP‐A, SP‐B, SP‐D), KL‐6 CCl6
2. Endothelium damage	Ang‐1, Ang‐2, ICAM‐1, selectins, VEGF, vWF
3. Lung extracellular matrix	Laminin, elastin, MMPs
B. Inflammation and inflammatory cascade
1. Proinflammatory cytokines	TNF‐α, IL‐1β, IL‐8/CXCL8, IL‐6, CCL‐2/MCP‐1, IL‐18
2. Antiinflammatory cytokines	IL‐10, sIL‐1RII, sTNF‐RI/sTNF‐II
3. Additional inflammatory markers	High mobility group box nuclear protein 1, lipopolysaccharide binding protein, nitric oxide, C‐reactive protein
C. Coagulation and fibrinolysis	Plasminogen activator inhibitor‐1, activated protein C, thrombomodulin, tissue factor, cell‐free hemoglobin
D. Pulmonary microvascular permeability vs. EF/PL protein ratio	EF/PL ratio
Fibroproliferative phase of ARDS (since day 7)
E. Endothelial proliferation	Vascular endothelial growth factor
F. Epithelial proliferation	Keratinocyte growth factor, hepatocyte growth factor
G. Apoptosis	Fas/FasL
H. Fibroblast proliferation	NT part of procollagen III (N‐PCP‐III)

RAGE, receptor for advanced glycation endproducts; HTI56, human type I cell‐specific membrane protein; SP, surfactant protein; KL‐6, Krebs von den Lungen‐6; CC16, Clara cells; Ang, angiopoietin‐1; ICAM‐1, intercellular adhesion molecule‐1; VEGF, vascular endothelial growth factor; vWF, von Willebrand factor; MMPs, matrix metalloproteinases; TNF‐ α, tumor necrosis factor‐α; IL, interleukin; sTNFR‐1, soluble tumor necrosis factor receptor‐1; sTNF‐II, soluble TNF receptor II; sIL‐1RII, soluble IL‐1 receptor II; MCP, monocyte chemoattractant protein; EF/PL ratio, fluid‐to‐plasma protein ratio; Fas/FasL.