Evaluation of Interrupter Resistance in Methacholine Challenge Testing in Children

摘要

Bronchial hyperresponsiveness (BHR) is a key feature of asthma and is assessed using bronchial provocation tests. The primary outcome in such tests (a 20% decrease in forced expiratory volume in 1 sec (FEV_1) is difficult to measure in young patients. This study evaluated the sensitivity and specificity of the interrupter resistance (R_(int)) technique, which does not require active patient participation, by comparing it to the primary outcome measure. Methacholine challenge tests were performed in children with a history of moderate asthma and BHR. Mean and individual changes in R_(int) and FEV_1 were studied. A receiver operating characteristic (ROC) curve was used to describe sensitivity and specificity of R_(int) Seventy-three children (median age: 9.2 years; range: 6.3-13.4years) participated. There was asignificant(P< 0.01) increase in mean R_(int) with increasing methacholine doses. However, individual changes of R_(int) showed large fluctuations. There was great overlap in change of R_(int) between children who did and did not reach the FEV_1 endpoint. A ROC curve showed an area under the curve of 0.65. Because of low sensitivity and specificity, the use of R_(int) to diagnose BHR in individual patients seems limited.