MMP9 and chronic obstructive pulmonary disease: Sputum cell MMP-9 expression levels [median (IQR)] normalized fluorescent intensity units]) were significantly greater in ex-smokers with COPD, [4622 (3161, 5962)], current smokers with COPD, [5085 (4378, 9338)] and healthy smokers, [4111 (1623, 6202)] compared with healthy never smokers, [1650 (1023, 3443)]; (p = 0.001 for each).