Assessment of severity measures for acute asthma outcomes: a first step in developing an asthma clinical prediction rule

Objective: As a first step in the development of an asthma prediction rule, our primary objective was to assess the association of 8 candidate predictor variables with 2 clinically relevant asthma outcomes. Methods: Among a cohort of 125 adults hospitalized with an asthma exacerbation, we examined models to identify clinical variables associated with length of stay (LOS) and clinically significant asthma exacerbations within 3 months after hospitalization (3-month exacerbation). Eight candidate predictor variables were chosen, including age, sex, race, pulsus paradoxus, prior endotracheal intubation for asthma, hospitalization within 5 years for asthma, and 2 chronic asthma severity scores. Results: We found independent associations between LOS and pulsus paradoxus (P = .005), prior intubation (P = .03), sex (P = .03), and prior hospitalization (P = .019). Among men, 52% had a 3-month exacerbation in comparison with 25% of women; and in multivariable analysis, male sex was independently associated with 3-month exacerbation (adjusted odds ratio = 5.1; 95% confidence interval = 1.37-18.9; P =.015). Participants with 3-month exacerbation had higher Johns Hopkins Allergy and Asthma Composite (JHAAC) chronic severity scores (median = 77; interquartile range = 57-91) than those who did not (median = 54; interquartile range = 35-69; P <.001) (for 40-unit increase, adjusted OR for 3-month exacerbation = 1.54; 95% confidence interval = 1.16-2.03; P =.003). In multivariable analysis, male sex and the JHAAC severity score were independently associated with 3-month exacerbation. Conclusions: Elevated pulsus paradoxus, prior intubation for asthma, and 5-year asthma hospitalization are independently associated with LOS. Race, 5-year asthma hospitalization, and JHAAC score predict 3-month asthma exacerbation. These variables warrant consideration for use in the development of an asthma prediction rule. (c) 2008 Elsevier Inc. All rights reserved.