RT Journal Article SR Electronic T1 Impulse oscillometry for leukotriene D4 inhalation challenge in asthma JF Respiratory Care FD American Association for Respiratory Care SP respcare.02417 DO 10.4187/respcare.02417 A1 Wei-jie Guan A1 Jin-ping Zheng A1 Yi Gao A1 Cai-yu Jiang A1 Xu Shi A1 Yan-qing Xie A1 Qing-xia Liu A1 Mei Jiang A1 Jia-ying An A1 Xin-xin Yu A1 Wen-ting Liu A1 Li-ping Zhong A1 Zhong-ping Wu A1 Nan-shan Zhong YR 2013 UL http://rc.rcjournal.com/content/early/2013/05/28/respcare.02417.abstract AB BACKGROUND: The significance of impulse oscillometry (IOS) parameters for bronchial provocation tests remains poorly defined. We aimed to investigate the positive threshold derived from the parameters and diagnostic power of IOS to asthma by using leukotriene D4 bronchial provocation test (LTD4-BPT). METHODS: Sixty-two patients with asthma and 21 healthy subjects were enrolled. The IOS was employed to perform LTD4-BPT followed by spirometry. The positive threshold was determined based on the cut-off point in receiver operation characteristic curve, by which the parameters of the highest diagnostic power were obtained. RESULTS: Of all IOS parameters, airway impedance at 5 Hz (Z5), resistance at 5 Hz (R5) and resonant frequency (Fres) were characterized by the highest diagnostic power (area under curve: 0.821, 0.815 and 0.806, respectively), with an increase of 57%, 43% and 63% corresponding to a 20% fall in FEV1, respectively. IOS indices yielded similar assay sensitivity and specificity with spirometry. The positive threshold of IOS, defined as either a 57% increase in Z5 or 63% increase in Fres for bronchial provocation test, yielded an assay accuracy of 0.6 in patients with asthma. CONCLUSIONS: IOS, when employed to conduct LTD4-BPT, is characterized by similar diagnostic power compared with spirometry. Either a 57% increase in Z5 or 63% increase in Fres may be regarded as a surrogate of FEV1 fall to determine airway hyperresponsiveness in asthma.