Subacute Lack of Asthma Control and Acute Asthma Exacerbation History as Predictors of Subsequent Acute Asthma Exacerbations: Evidence From Managed Care Data

BACKGROUND: Monitoring indicators of subacute lack of asthma control (SALAC) may help to reduce asthma morbidity. OBJECTIVE: To determine whether SALAC, independent of current asthma exacerbations, is associated with subsequent acute asthma exacerbations. METHODS: Administrative claims data from PharMetrics/IMS Health were used to identify patients 12 years or older continuously enrolled in a participating U.S. health plan from 2001 to 2004 with >or=1 asthma claim (International Classification of Diseases, Ninth Revision, Clinical Modification code 493.x), no chronic obstructive pulmonary disease or cystic fibrosis claims, and >or=1 prescription for an asthma medication during 2001-2004. SALAC was defined as more than 4 asthma-related physician visits (or >or=2/quarter) or more than 5 short-acting beta((2))-adrenergic agonist prescriptions during 2001. Effect of asthma control category (Exacerbation Only EO, SALAC Only SO, Both Exacerbation and SALAC Both, Neither Exacerbation nor SALAC Neither) in 2001 on acute asthma exacerbations (hospitalization, emergency department visit, or short-term oral corticosteroid use) during 2002-2004 was assessed using logistic regression, adjusting for gender, age, health plan type, and region. RESULTS: Of 11,779 patients, 8% were assigned to the EO group, 26% to SO, 12% to Both, and 54% to Neither in 2001. The incidence of exacerbations in 2002-2004 was higher for Both (61.8%) versus EO (55.0%) and for SO (37.3%) versus Neither (31.9%). The risk of exacerbation in 2002-2004 was increased significantly (p < .0001) for Both (3.394; 95% confidence interval CI = 3.009, 3.827), EO (2.503; 95% CI = 2.176, 2.879), and SO (1.277; 95% CI = 1.166, 1.399) versus Neither. CONCLUSION: In this study, the risk of subsequent exacerbation was greatest in patients with both SALAC and acute asthma exacerbations, followed by those with exacerbations only and those with SALAC only. SO identified an additional 26% of asthma patients at increased risk for subsequent exacerbation. The results from this study demonstrate that SALAC indicators and a history of acute asthma exacerbations are independent predictors of future acute asthma exacerbations and highlight the important role of subacute asthma worsening in predicting and preventing future asthma exacerbations.