Assessment of Airway Hyperresponsiveness: Comparison of Spirometry and Body Plethysmography

Abstract

While methacholine (MCH) testing is commonly used in the clinical diagnosis of asthma, the detection of airway narrowing often relies on either spirometry or body plethysmography, however comparative studies are rare. In this study we performed MCH testing in 37 patients with variable shortness of breath at work and in 37 patients with no history of airway disease. The inclusion criteria were: no acute respiratory infection within 6 weeks, no severe diseases, normal baseline specific airway resistance (sR(aw)), normal baseline forced expiratory volume in 1 s (FEV(1)), Tiffeneau index >70%, no previous treatment with steroids within 14 days and no short acting bronchodilators within 24 h. Cumulative doses of 0.003, 0.014, 0.059, 0.239 and 0.959 mg MCH were inhaled by a dosimeter method. A FEV(1) decrease of ≥20% from baseline and a 100% increase of sR(aw) to ≥2.0 kPa/s was defined as end-of-test-criterion. Provocation doses were calculated by interpolation. Performance of lung function parameters was compared using receiver-operating-characteristic (ROC) analysis. ROC analysis resulted in an area under the ROC curve (AUC) of 0.74 for FEV(1) vs. 0.82 for sR(aw). The corresponding Youden Indices (J) were 0.46 for FEV(1) and 0.57 for sR(aw). The Youden Index of sR(aw) was higher and sensitivity and specificity (73%/84%) were rather well-balanced, in contrast to FEV(1) (54%/92%). In conclusion, in cumulative MCH challenges sR(aw) was found to be the overall most useful parameter for the detection of bronchial hyperresponsiveness. Body plethysmography yielded a balanced sensitivity-specificity ratio with higher sensitivity than spirometry, but comparable specificity.

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

“…Second, the broncho-provocating process by MCH in relation to the development of pulmonary hyperinflation and/or the phenomenon of dysanapsis, the ratio FEF 25–75 /FVC thought to be a surrogate measure of airway size relative to lung size significantly associated with AHR [44]. The present study positively confirms the findings of Nensa et al [10] reinforcing sR eff , and its reciprocal value sG eff respectively, as the most useful target parameters in the detection of AHR. Due to our observations of much higher percent-response to MCH by PD −40 sG eff than by PD −20 FEV 1 , we suggest, that some false negative PD −20 FEV 1 tests resulted in an underestimation of the severity of AHR, and hence potentially missed the diagnosis of asthma.…”

“…The principal goal of our study was to demonstrate that the performance of MCTs using the plethysmographic technique in addition to the spirometric approach offers some fundamental benefits, such as independence from deep inspiration, and hence, modulation of the airway calibre [10, 31–36], avoidance of forced expiratory manoeuvres, and hence the subject’s cooperation and coordination, which is known to change the airway responsiveness during the test procedure [34, 37, 38]. There are two important denouements, which are achieved, if the spirometric assessment of AHR is combined with whole-body plethysmography.…”

“…Details are given in the Additional file 1. Our anticipated advantages, therefore, were to elaborate, whether or not in comparison to the spirometric approach, the new plethysmographic technology could provide ( i ) better diagnostic accuracy, ( ii ) leading by independency of deep inspirations and hence changes in the volume-history [10, 31–36] to less “a priori” modulation of the airway calibre, moreover, ( iii ) by independency from the subject’s cooperation (need of forced breathing manoeuvres) circumvention of inadvertent change of the airway responsiveness during test procedure [34, 37, 38]. …”

“…Airway hyperreactivity (AHR) is a characteristic feature of bronchial asthma, and methacholine challenge testing (MCT) is well established to quantitate AHR in patients with unexplained symptoms such as cough, chest tightness and/or dyspnea, when the diagnosis of asthma is uncertain [1–10]. Compared to control subjects the provoked bronchial obstruction appears earlier and at lower provocation doses, and is more intensive in patients with asthma, a functional feature serving as rationale for the underlying mechanisms of AHR [4, 11, 12].…”

“…Alternatively, whole-body plethysmography can also be used to determine AHR, measuring changes in airway mechanics either by a 35% [2, 7], a 40% [4, 5], or a 50% [5] reduction in specific airway conductance (sG aw ) or an increase of specific airway resistance (sR aw ) of 100% [8, 10] from baseline. To our knowledge, studies comparing reliability of spirometric parameters with those obtained by whole-body plethysmography, or even a combination of both are rare, and the so-called effective specific airway conductance (sG eff ) has never been evaluated as a target parameter.…”