Bronchial Lability Index in the Diagnosis of Asthma in Children

Abstract

Asthma diagnosis is usually confirmed by either bronchoprovocation or bronchodilation tests. In the present study, we used these tests combined with calculated bronchial lability indices (BLIs). Fifty children were examined by free-running and bronchodilation tests, as well as by home peak expirating flow (PEF) monitoring. Ventilatory functions were followed with a Wright peak expiratng flow (WPEF) meter, and asthma was diagnosed if at least one of these three tests was positive. The exercise challenge and bronchodilation tests were also monitored by forced expiratory volume in 1 second (FEV1) and interrupter resistance (Rint), but the results obtained from these measurements did not influence the diagnosis of asthma. The BLIs were calculated for FEV1 and Rint as the sum of the percentage of change induced by free running and bronchodilator inhalation. Asthma was diagnosed by WPEF in 26 (52%) children: 85% had a diagnostic finding in the home PEF monitoring, 62% in the exercise challenge, and 31% in the bronchodilation test. By using the limit of 8% in FEV1 BLI and 30% in Rint BLI, the FEV1 BLI was positive in 20 (77%) of the asthma cases and the Rint BLI was positive in 19 (73%) of the asthma cases. The specificity of the BLIs was 92% by FEV1 and 75% by Rint. The exercise challenge and bronchodilation tests measured by FEV1 (8% limit in both) were positive equally often in 8 (31%) of the asthmatic children. The respective figure for Rint was 10 (39%) in both tests (15% increase in the exercise challenge test and 30% decrease in the bronchodilation test). By using the exercise challenge or bronchodilation test separately, we could diagnose fewer than half of the asthmatic children. In contrast, by using the BLIs, over 70% of the asthmatics were identified. We conclude that the calculation of BLIs should be included in the diagnosis of asthma in children.