PT  - JOURNAL ARTICLE
AU  - Wei-jie Guan
AU  - Jin-ping Zheng
AU  - Yi Gao
AU  - Cai-yu Jiang
AU  - Xu Shi
AU  - Yan-qing Xie
AU  - Qing-xia Liu
AU  - Mei Jiang
AU  - Jia-ying An
AU  - Xin-xin Yu
AU  - Wen-ting Liu
AU  - Li-ping Zhong
AU  - Zhong-ping Wu
AU  - Nan-shan Zhong
TI  - Impulse oscillometry for leukotriene D<sub>4</sub> inhalation challenge in asthma
AID  - 10.4187/respcare.02417
DP  - 2013 May 28
TA  - Respiratory Care
PG  - respcare.02417
4099  - http://rc.rcjournal.com/content/early/2013/05/28/respcare.02417.short
4100  - http://rc.rcjournal.com/content/early/2013/05/28/respcare.02417.full
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.