Bronchial lability index in the diagnosis of asthma in children

Asthma diagnosis is usually confirmed by either bronchoprovocation or bronc hodilation tests. In the present study, we used these tests combined with c alculated bronchial lability indices (BLIs). Fifty children were examined b y free-running and bronchodilation tests, as well as by home peak expiratin g 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 bronchodilati on tests were also monitored by forced expiratory volume in 1 second (FEV1) and interrupter resistance (R-int), but the results obtained from these me asurements did not influence the diagnosis of asthma. The BLIs were calcula ted for FEV1 and R-int as the sum of the percentage of change induced by fr ee running and bronchodilator inhalation. Asthma was diagnosed by WPEF in 2 6 (52 %) children: 85% had a diagnostic finding in the home PEF monitoring, 62% in the exercise challenge, and 31% in the bronchodilation test. By usi ng the limit of 8% in FEV1 BLI and 30% in R-int BLI, the FEV1 BLI was posit ive 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 R-int. The exercise challenge and bronchodilation tests measured by FEV 1 (8% limit in both) were positive equally often in 8 (31%) of the asthmati c children. The respective figure for R-int was 10 (39%) in both tests (15% increase in the exercise challenge test and 30% decrease in the bronchodil ation test). By using the exercise challenge or bronchodilation test separa tely, we could diagnose fewer than half of the asthmatic children. In contr ast, by using the BLIs, over 70% of the asthmatics were identified. We conc lude that the calculation of BLIs should be included in the diagnosis of as thma in children.