The strategy for predicting future exacerbation of asthma using a combination of the Asthma Control Test and lung function test.

BACKGROUND: Various factors have been reported to be useful for predicting future exacerbations.
OBJECTIVE: This study was intended to determine a usefulness of a combination of a patient-based questionnaire, such as the Asthma Control Test (ACT) score with objective assessments, such as forced expiratory volume in 1 second (FEV(1)) and/or exhaled nitric oxide (FE(NO)), for predicting future exacerbations in adult asthmatics.
METHODS: We therefore enrolled 78 subjects with mild to moderate asthma, who were clinically stable for 3 months who all had been regularly receiving inhaled steroid treatment. All subjects underwent a routine assessment of asthma control including the ACT score, spirometry, and FE(NO), and then were followed up until a severe exacerbation occurred. The predictors of an increased risk of severe exacerbation were identified and validated using decision trees based on a classification and regression tree (CART) analysis. The properties of the developed models were the evaluated with the area under the ROC curve (AUC) (95% confidence interval [CI]).
RESULTS: The CART analysis automatically selected the variables and cut-off points, the ACT score <or=23 and FEV(1) <or= 91.8%, with the greatest capacity for discriminating future exacerbations within one year or not. When the probability was calculated by the likelihood ratio of a positive test (LP), the ACT score <or=23 was identified with a 60.3% probability, calculated by 1.82 of LP, whereas the combined ACT score <or=23 and the percentage of predicted FEV(1) <or= 91.8% were identified with an 85.0% probability, calculated by an LP score of 5.43, for predicting future exacerbation.
CONCLUSION: These results demonstrated that combining the ACT score and percentage of predicted FEV(1), but not FE(NO,) can sufficiently stratify the risk for future exacerbations within one year.