Measurement of the peak expiratory flow (PEF) is ideal for patients to perform at home for objective monitoring of chronic asthma. The level of eosinophil cationic protein (ECP) in induced sputum has been reported to be a reliable parameter of airway inflammation. Accordingly, we investigated the relationship between ECP level in induced sputum and management of asthma by the PEF zone system. Sixteen asthma outpatients were enrolled in this study which was performed over a 6 month period. PEF

more »

... nes were determined from the personal-best weekly mean PEF value during the initial 3 months. During the next 3 months, the inhaled corticosteroid (ICS) dose was reduced by 50% and the rate required to maintain the PEF green zone set in the first 3 months was calculated. The eosinophil count and ECP level in induced sputum, as well as the serum ECP level, were measured 3 times throughout the study period. In the steroid group, there was a significant decrease in the PEF green zone maintenance rate, but no significant changes in the sputum eosinophil count, sputum ECP level and serum ECP level. There was no significant relationship between the PEF green zone maintenance rate and the sputum ECP level. Although the PEF green zone maintenance rate reflected the clinical response to ICS dose reduction, the ECP level (sputum or serum) was much less sensitive. This suggests that ECP may be of limited value for monitoring airway inflammation in patients with chronic stable asthma on anti-inflammatory therapy.