Short-acting beta-agonist prescription fills as a marker for asthma morbidity

Hospital admissions and emergency department (ED) visits have traditionally been used to assess the strength of association between environmental exposures, such as air pollution, and asthma morbidity. In the current study, we evaluate the use of short-acting beta-agonist (SABA) prescriptions as a surrogate marker for asthma exacerbation with respect to these more traditional markers.

Claims data for recipients covered by Illinois Medicaid with a diagnosis of asthma were obtained for fiscal-years 1996 through June 1998. Claims for short-acting bronchodilators and asthma-related ED visits and hospital admissions for 31,140 adults were identified. The odds ratio for the association of either an ED visit or hospital admission and an SABA prescription was calculated for time lags ranging from -28 to +28 days. Individual-subject heterogeneity and seasonal effects were corrected for using the Mantel-Haenszel method.

After adjustment for individual and seasonal effects, there was a significant positive association between SABA prescriptions and ED visits or hospital admissions for asthma on any single day. In addition, a significant positive association was also found between the ED visits or hospital admissions occurring on the few days prior to an SABA prescription. No significant relation was found (after adjusting for subject and seasonal effects) between prescriptions and admissions when an SABA prescription date preceded that of a hospital admission or an ED visit.

A very strong and significant association between ED visits or hospital admissions for asthma and SABA prescriptions was observed, which suggests that SABA prescription fills can be used as a marker for asthma morbidity. In addition, a temporal association exists between claims for ED visits or hospital admissions for asthma and SABA prescription claims when an ED visit or hospital admission precedes the SABA prescription.