We therefore performed the first meta-analysis of published studies examining sputum MPO in COPD patients to determine: 1) whether the MPO level is increased in COPD patients compared to healthy subjects or asthmatics; 2) whether there is a difference in MPO level between patients with stable disease and during acute exacerbation; and 3) whether anti-inflammatory treatment could reduce the MPO level. The gene discussed is MPO; the disease is chronic obstructive pulmonary disease.