The following is a summary of “Presence of variable extrathoracic airflow limitation in patients with a negative methacholine challenge test,” published in the November 2023 issue of Allergy & Immunology by Elfessi et al.
The study aimed to investigate the presence of variable extrathoracic airflow limitation (VEAL) in patients with negative methacholine challenge tests (MCT).
The electronic medical records of individuals who underwent MCT at Jesse Brown VA Medical Center from January 2017 to December 2019 were examined. Only patients with negative MCT results were included. Relevant demographic, clinical, and pulmonary function test (PFT) data and MCT results were extracted. A co-author reviewed spirometric flow-volume loops from each test to identify the first methacholine concentration at which FEF50/FIF50 exceeded 1 or further increased if the baseline FEF50/sub>/FIF50/sub> after nebulized saline already exceeded 1. Statistical analysis utilized Student’s t-test, with significance set at P < 0.05.
Among 127 patients with normal baseline PFT and negative MCT, 10.2% (13 patients) exhibited negative MCT and FEF50/sub>/FIF50/sub> > 1 after testing. This subgroup, predominantly comprising non-smoking, obese, white males with a mean age of 51.3 ± 14.1 years, was referred for symptoms indicative of asthma or chronic cough. Additional comorbidities included obstructive sleep apnea, gastroesophageal reflux disease, and chronic rhinosinusitis. FEF50/sub>/FIF50/sub> increased significantly from 0.72 ± 0.21 after nebulized saline to 1.21 ± 0.13 after inhaled methacholine (p < 0.001). The median inhaled methacholine concentration eliciting these responses was 1.0 mg/mL (range, 0.25–16 mg/mL).
The study identified VEAL in a subset of patients with negative MCT. Recognition and reporting this phenomenon to healthcare providers are crucial, and its clinical significance should be addressed as needed.
Source: aacijournal.biomedcentral.com/articles/10.1186/s13223-023-00860-w
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