With a mean interval of 4.4?y after the last visit, 137 subjects (67 % of the original CATO population) participated in this follow-up study. Evaluation consisted of spirometry (n?=?137), a methacholine challenge test (n?=?83), data on inhaled steroid treatment and asthma exacerbations (n?=?137), and an asthma symptom diary during 6 weeks (n?=?90).
At follow-up, lung function, % symptom-free days and exacerbation rates of both treatment strategy groups was similar. The mean dose of inhaled corticosteroids had diminished from 550?¦Ìg/day at the end of CATO to 235?¦Ìg/day at follow-up. The decrease in AHR measured at the end of CATO was maintained at follow-up for both treatment strategy groups.
The beneficial effect on lung function of 2 years treatment guided by AHR was lost after 3-7 years of usual care. This suggests that an AHR-guided treatment strategy may need to be sustained in order to preserve lung function.