A Prospective Observational Study in a Tertiary Pediatric Hospital in Beijing to Understand the Accuracy of Bronchodilator Response (BDR) in Chinese Controller Naive Asthmatic Children Between the Age of 4~12 Years Old

Objectives:

1. To observe BDR distribution curve for Chinese non-asthmatic and controller-naïve asthmatic children from 4-12 years respectively
2. To compare BDR values between non-asthmatic group and controller-naïve asthmatic group, and analyze appropriate cut-off point value

Background and rationale:

According to the guidelines spirometry, including baseline forced expiratory volume in 1 second (FEV1) and the bronchodilator response (BDR) to short acting beta agonists (SABA), should be used in children as objective measures to establish the diagnosis and severity of bronchial asthma. Baseline FEV1 is usually in the normal range (greater than 80% predicted) in children, regardless of asthma severity, so several other objective measures have been suggested for diagnosis in children, including the response to a bronchodilator, which reflects airway reversibility.

The current definition for a positive BDR is >12% reversibility. In the study carried out by Galant et al among 51 non-asthmatic children and 346 controller naïve asthmatic children between 4-17 years, the BDR value could achieve 12% in only 30.6% asthmatic children, across all severity. Also, in a study among 142 children between 5-10 years in UK, 9% increase in FEV1 after bronchodilator use was suggested as the cutoff point with good sensitivity and specificity.

Difference between the proposed study to be carried out in our hospital and the one in Anhui Province is that we will tentatively calculate a BDR cutoff point by using receiver operating characteristic (ROC curve). And the cutoff point can be used as a reference indicator in asthma diagnosis and long-term management.

The current BDR cutoff point of 12% that is not ideal for children can also be reflected in the clinical management. It has been shown that a persistent BDR value, even less than 12%, in asthmatic children suggests poor clinical outcome. In a 4 years study among 1041 asthmatic children in America carried out by Sharma et al, it showed that compared with individuals who had a BDR of 12% and 200ml, individuals who had a BDR of 10% had similar poor clinical outcomes (e.g. more hospital visits, more prednisone bursts, increased nocturnal awakenings, and missing more days of school). Same results were also obtained in Galant et al study among 679 asthmatic children among 5-18 years.