Variability of symptoms in mild persistent asthma: baseline data from the MIAMI study.

Objective: To describe the variability of the asthma phenotype in patients with mild persistent asthma enrolled in the Mild Asthma Montelukast versus Inhaled Corticosteroid (MIAMI) study.

Methods: The variability of asthma rescue-free days, asthma symptoms, albuterol use, medical resource use, and exercise Limitations among patients with documented mild persistent asthma was compared between the month before study enrollment and the last 2 weeks of the run-in period.

Results: Patients eligible for randomization (n = 400), aged 15-85 years, exhibited symptoms (mean +/- SD) 3.6 +/- 1.3 days/week, beta-agonist use 3.5 +/- 1.3 days/week, and normal FEV1 (94.0 +/- 9.9% predicted) during the last 2 weeks of the run-in period. In the year before enrollment, medical intervention for asthma flares was common: 38.5% made office visits, 15.8% had oral corticosteroids, and 8.3% required emergency room or hospitalized care. In the month before enrollment, 11.8% experienced daily symptoms, and 28.3% had limitations of normal activity. Patients with daily symptoms in the month before study enrollment, compared with those having less-than-daily symptoms, experienced fewer rescue-free days (P = 0.024) and had more days per week with symptoms (P = 0.008) and requiring albuterol (P = 0.048) during the run-in; FEV1 was similar for both groups (93.1% vs. 94.2% predicted, respectively).

Conclusion: Patients with mild persistent asthma reported a substantial disease burden in the year before enrollment. The asthma burden experienced by these patients both before and during the run-in period was of sufficient severity to support the recommendation that mild persistent asthma should be managed with daily controller therapy.