PTX3 and infection: Previous studies in non-COPD cohorts have shown PTX3 to rapidly increase due to an infection.19,33 PTX3 has been shown to be elevated in COPD subjects compared with healthy controls in plasma34 and sputum.35 PTX3 levels have been correlated with the number of neutrophils present in sputum and have been shown to be elevated in current and ex-smokers compared with non-smokers.36 Our results support these statements.