For the purposes of prediction and planning, such as might be undertaken by a health system or health maintenance organization, a disadvantage of the NAEPP multifaceted approach to rating severity is that it does not separate asthma outcomes (eg, symptoms) from objective markers of disease severity. Our analysis focused on the validation of one potential marker of risk of subsequent asthma attacks. Of interest, a study by Tattersfield et al34 examined multiple factors for their association with exacerbations occurring in a cohort of subjects with persistent asthma. They reported that in 12 months of follow-up, female gender, increasing age, PEF variability during the run-in period, and inhaled corticosteroid dose before study onset were positively associated with the risk of exacerbation. The authors report that for a 1% increase in PEF variability, a 100-μg increase in prestudy inhaled corticosteroid dose, and a 1-year increase in age, the ORs for having an exacerbation were 1.023 (95% CI, 1.011 to 1.035), 1.056 (95% CI, 1.016 to 1.096), and 1.011 (95% CI, 1.001 to 1.023), respectively. The study published by Tattersfield et al34 differed from ours, however, in that the measure of lung function examined was PEF and not FEV1% predicted, and their outcome was not self-report of an asthma attack but rather an exacerbation defined as a worsening of asthma control requiring oral corticosteroids or as an episode in which morning PEF fell by > 30% from baseline on 2 consecutive days.