Abstract
BackgroundMethacholine challenge tests (MCTs) are used to diagnose airway hyperresponsiveness (AHR) in patients with suspected asthma where previous diagnostic testing has been inconclusive. The test is time consuming and usually requires referral to specialized centers. Simple methods to predict AHR could help determine which patients should be referred to MCTs, thus avoiding unnecessary testing. Here we investigated the potential use of baseline spirometry variables as surrogate markers for AHR in adults with suspected asthma.MethodsBaseline spirometry and MCTs performed between 2013 and 2019 in a large tertiary center were retrospectively evaluated. Receiver-operating characteristic curves for the maximal expiratory flow-volume curve indices (angle β, FEV1, FVC, FEV1/FVC, FEF50%, FEF25–75%) were constructed to assess their overall accuracy in predicting AHR and optimal cutoff values were identified.ResultsA total of 2983 tests were analyzed in adults aged 18–40 years. In total, 14% of all MCTs were positive (PC20 ≤ 16 mg/ml). All baseline spirometry parameters were significantly lower in the positive group (p < 0.001). FEF50% showed the best overall accuracy (AUC = 0.688) and proved to be useful as a negative predictor when applying FEF50% ≥ 110% as a cutoff level.ConclusionsThis study highlights the role of FEF50% in predicting AHR in patients with suspected asthma. A value of ≥ 110% for baseline FEF50% could be used to exclude AHR and would lead to a substantial decrease in MCT referrals.
Highlights
Methacholine challenge tests (MCTs) are used to diagnose airway hyperresponsiveness (AHR) in patients with suspected asthma where previous diagnostic testing has been inconclusive
Comparison of characteristics in derivation and validation cohort There was no significant difference in clinical characteristics at baseline between the derivation and validation cohorts (Table 1 according to European Community of Coal and Steel (ECCS) equations, Additional file 1: Table S1 according to Global Lung Function Initiative (GLI) equations and z-scores; there is no reference for FEF50% in the GLI, both FEF50% and the angle β, which is based on FEF50%, are not shown for GLI-based spirometry parameters)
Positive versus negative methacholine challenge test groups: baseline comparisons In order to determine which clinical parameters might have a predictive value, the derivation cohort was stratified depending on outcome in the MCT and comparisons between the two groups were conducted (Table 2 according to ECCS equations, Additional file 1: Table S2 according to GLI equations and z-scores)
Summary
Methacholine challenge tests (MCTs) are used to diagnose airway hyperresponsiveness (AHR) in patients with suspected asthma where previous diagnostic testing has been inconclusive. Methacholine challenge tests (MCTs) are used to detect and assess airway hyperreactivity (AHR). Peled et al BMC Pulm Med (2021) 21:153 the forced expiratory flow rate between 25 and 75% of vital capacity (FEF25–75%) and at 50% of vital capacity (FEF50%). They are considered approximate measures of the flow in the peripheral airways and a reduction in either variable may represent airflow limitation in the small airways [3, 4]. No studies have investigated the predictive ability of these variables in a general population consisting of both asthmatics and healthy individuals
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