Table 4 Studies assessing biomarkers for their potential to provide clinically relevant information

Clinical variables

Symptoms at ECOPD onset

FeNO[14], EBC: H₂O₂[28], IS: IL-6[53], Nasal wash: IL-6[46], IL-8[46]

Clinical severity

EBC: CysLTs[29], H₂O₂[29], 8-isoprostane[29], LTB₄[29], PGE₂[29]

SS: lactoferrin[40], LL-37[40], lysozyme[40], NE[31, 38], SLPI[40]

Large airway secretions: IL-8[65], TNF-α[65]

PFTs

FeNO[10, 12, 13, 20]

EBC: CysLTs[29], H₂O₂[29], 8-isoprostane[29], IL-8[25], LTB₄[29], MPO[23], PGE₂[29], pH[13], SLPI[23]

IS/SS: IL-6[63], IL-8[63]

ABG analysis

FeNO[13]

EBC: pH[13]

Prediction of clinical outcomes

Symptomatic recovery

SS: IL-8[39, 41], NE[39], TNF-α[39]

Length of hospital stay

FeNO[12]

Causal diagnosis

FeNO[18]

SS: IL-1β[48], IL-8[38, 46, 48], LL37[40], lysozyme[40], NE[38, 39], SLPI[40], TNFα[38, 39, 48]

IS: IL-6[54, 56, 57], IL-8[55–57], LTB4[57], MPO[55, 57], NE[56], TNF-α[55–57]

IS/SS: IL-1β[59], IL-8[63, 64], TNF-α[64]

NW: IL-6[46]

BAL: IL-6[68], IL-8[68], NE[68]

Response to treatment

FeNO[10, 15]

EBC: Cys-LTs[29], H₂O₂[29], IL-6[31], 8-isoprostane[29, 31], LTB₄[29], PGE₂[29], TNFα[24, 36]

IS: IL-8[15], TNFα[15, 34, 36]