MPO and chronic obstructive pulmonary disease: The SMD of MPO in COPD patients before and after glucocorticoid treatment was 0.05 (95% CI-1.02 to 1.13, P = 0.921; I2 = 88.7%; random effects model) indicating that glucocorticoids had no effect on MPO levels in sputum of COPD patients (Figure 7).