• Yi-Han Hsiao, Yu-Jung Lin, Tien-Hsin Jeng, Kang-Cheng Su, Hsin-Kuo Ko, Sheau-Ning Yang, Diahn-Warng Perng, and Yu Ru Kou.
• Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan, ROC.
• J Chin Med Assoc. 2022 Aug 1; 85 (8): 859-865.

BackgroundIdentifying positive bronchodilator reversibility (BDR) helps the diagnosis of asthma. However, not all patients can adequately perform the forced expiration during the spirometry test. An alternative test is required. Impulse oscillometry (IOS) is an effort-independent technique that enables the measurement of lung mechanics during quiet tidal breathing. We investigated the potentiality of IOS to evaluate BDR in untreated adult patients with newly diagnosed asthma (UAPNDS).MethodsAll UAPNDS (aged 20-80 years) who never smoke and underwent IOS and spirometry before and after salbutamol inhalation at their initial visit to the hospital from March 22, 2017, to December 31, 2019, were identified. A total of 323 patients were enrolled. Data from the medical record, including demographic characteristics, laboratory examination, spirometric data, and IOS parameters, were retrospectively reviewed. The associations of parameters with the positive BDR and the performance of parameters in predicting the positive BDR were evaluated by statistical methods.ResultsPatients (n = 323) had a median age of 64 years and were mostly female (67.5%). Several variables, including serum total immunoglobulin level, blood eosinophil counts, blood eosinophil percentage (%), and two IOS parameters, were found to be different between the positive (n = 93) and negative BDR (n = 230) groups. Multivariate logistic regression analyses after adjustment by cofactors revealed that the percentage change of the area under the reactance curve between 5 Hz and resonant frequency [ΔAx (%)] after salbutamol inhalation was the only independent factor for the positive BDR. The area under the receiver operating characteristic curve of ΔAx (%) in predicting the positive BDR was 0.614 ( p = 0.0013), and its optimal cutoff value was -53.8% (sensitivity, 39.78% and specificity, 80.43%).ConclusionIn addition to spirometry, ΔAx (%), an IOS parameter, may serve as a novel indicator to evaluate BDR in UAPNDS.Copyright © 2022, the Chinese Medical Association.

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