Background: Previous studies indicate that the percent recovery index (PRI: the percentage increase from the maximally reduced FEV1 after bronchodilator inhalation), one of the indexes of methacholine bronchial provocation, may predict acute asthma exacerbations in childhood and elderly asthmatics. It is known that childhood (< 12) and elder (> 60) asthmatics may be different to adult patients in many aspect including prognosis. However, in adults, a research for predicting value of PRI to exacerbation is still absence. Besides exacerbation, predicting value of PRI to poor asthma control is also unknown. We try to detect whether PRI can predict poor asthma control and exacerbation in adults in this research. Meanwhile, we try to detect whether treatment can influence PRI.
Methods: In 61 adults with asthma, baseline PRI was measured during enrollment. And then baseline PRI was evaluated as a predictor of exacerbation or poor asthma control at an upcoming 3-month follow-up. The covariates included age, sex, BMI, previous exacerbation, smoking status and baseline lung function. After treatment for 3 months, PRI was measured again and compared with baseline PRI.
Results: After the 3-month follow-up, we found that baseline PRI was significantly related to asthma exacerbation (P = 0.023), poor asthma control (ACT at 3 months, P = 0.014), decreased quality of life (decrease of MiniAQLQ, P = 0.010) and cumulative number of EDHO at 3 months (P = 0.039). Meanwhile, no significant correlation was observed between baseline PRI and inflammation factors (FENO, CaNO, and EOS). Finally, PRI was dramatically reduced after standard treatment for 3 months.
Conclusion: PRI is efficient in the prediction of poor asthma control and exacerbation in adults. The predictive value of PRI may rely on the inherent property of asthmatic airway smooth muscle (ASM) independent of inflammation factors. Effective treatment can alleviate PRI dramatically and that indicate PRI may also be valuable in evaluation of curative effect.
Keywords: asthma, exacerbation, poor control, percent recovery index, bronchodilator reversibility