Correlation between Reduced FEF25-75% and a Positive Methacholine Challenge Test in Adults with Nonobstructive...

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• Nonobstructive spirometry is common, but some individuals may still exhibit airway hyperresponsiveness.
• The mid-expiratory flow rate (FEF25-75%) is a sensitive but often overlooked parameter in spirometry.

Purpose of the Study:

• To investigate the association between a reduced FEF25-75% and a positive methacholine challenge test (MCT) in adults with nonobstructive baseline spirometry.
• To determine if FEF25-75% can predict airway hyperresponsiveness in this population.

Main Methods:

• Retrospective analysis of patients undergoing MCT with nonobstructive spirometry (April 2014 - January 2020).
• Logistic regression used to assess the relationship between FEF25-75% and MCT outcome, adjusting for age, gender, BMI, FEV1, and FEV1/FVC.

Main Results:

• Out of 496 patients, 187 (38%) had a positive MCT. Patients with a positive MCT were younger (mean age 32 vs. 38 years).
• Mean FEF25-75% was significantly lower in patients with a positive MCT (3.12 L/s) compared to those with a negative MCT (3.39 L/s).
• Logistic regression showed an inverse relationship between FEF25-75% and MCT positivity (OR=0.90 per % predicted increase), indicating reduced FEF25-75% predicts a positive MCT, particularly in younger individuals.

Conclusions:

• A reduced FEF25-75% in adults with nonobstructive spirometry is a predictor of a positive methacholine challenge test.
• This predictive relationship is more pronounced in younger adults and diminishes with increasing age.