MPO and asthma: Abbreviations; ACT: asthma control test, ANCA: anti-neutrophil cytoplasmic antibody, CRP: C-reactive protein, FeNO: fractional exhaled nitric oxide, FEV1: forced expiratory volume in 1 s, MPO: myeloperoxidase, N/A: not available, TARC: thymus and activation-regulated chemokine, PEF: peak flow, VAS: visual analogue scale, WBC: white blood cell