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Background  There are few studies comparing diagnostic accuracy of different lung function parameters evaluating dose–response characteristics of methacholine (MCH) challenge tests (MCT) as quantitative outcome of airway hyperreactivity (AHR) in asthmatic patients. The aim of this retrospectively analysis of our database (Clinic Barmelweid, Switzerland) was, to assess diagnostic accuracy of several lung function parameters quantitating AHR by dose–response characteristics.    Methods  Changes in effective specific airway conductance (sG eff ) as estimate of the degree of bronchial obstruction were compared with concomitantly measured forced expiratory volume in 1 s (FEV 1 ) and forced expiratory flows at 50% forced vital capacity (FEF 50 ). According to the GINA Guidelines the patients ( n  = 484) were classified into asthmatic patients ( n  = 337) and non-asthmatic subjects ( n  = 147). Whole-body plethysmography (CareFusion, Würzburg, Germany) was performed using ATS-ERS criteria, and for the MCTs a standardised computer controlled protocol with 3 consecutive cumulative provocation doses (PD 1 : 0.2 mg; PD 2 : 1.0 mg; PD 3 : 2.2 mg) was used. Break off criterion for the MCTs were when a decrease in FEV 1  of 20% was reached or respiratory symptoms occurred.    Results  In the assessment of AHR, whole-body plethysmography offers in addition to spirometry indices of airways conductance and thoracic lung volumes, which are incorporated in the parameter sG eff , derived from spontaneous tidal breathing. The cumulative percent dose-responses at each provocation step were at the 1 st  level step (0.2 mg MCH) 3.7 times, at the 2 nd  level step (1 mg MCH) 2.4 times, and at the 3 rd  level step (2.2 mg MCH) 2.0 times more pronounced for sG eff , compared to FEV 1 . A much better diagnostic odds ratio of sG eff  (7.855) over FEV 1  (6.893) and FEF 50  (4.001) could be found. Moreover, the so-called dysanapsis, and changes of end-expiratory lung volume were found to be important determinants of AHR.    Conclusions  Applying plethysmographic tidal breathing analysis in addition to spirometry in MCTs provides relevant advantages. The absence of deep and maximal inhalations and forced expiratory manoeuvres improve the subject’s cooperation and coordination, and provide sensitive and differentiated test results, improving diagnostic accuracy. Moreover, by the combined assessment, pulmonary hyperinflation and dysanapsis can be respected in the differentiation between “asthmatics” and “non-asthmatics”.    Electronic supplementary material  The online version of this article (doi:10.1186/s12931-016-0470-0) contains supplementary material, which is available to authorized users.

Diagnostic accuracy of methacholine challenge tests assessing airway hyperreactivity in asthmatic patients - a multifunctional approach