Abstract
Objective To clarify whether in adults with a nonobstructive spirometry a reduced FEF25-75% is associated with a positive methacholine challenge test (MCT). Methods Data was collected for all the patients who had a MCT done between April 2014 and January 2020 but had nonobstructive baseline spirometry. Logistic regression was utilized to estimate the log odds of a positive methacholine test as a function of FEF25-75% and also for age, gender, BMI, FEV1, and FEV1/FVC. Results Out of 496 patients, 187 (38%) had a positive MCT. Baseline characteristics in two groups were similar except that patients with positive MCT were younger (32 ± 11.57 vs. 38 ± 13.25 years, respectively, p < 0.001). Mean FEF25-75% was lower in MCT positive (3.12 ± 0.99 L/s) vs. MCT negative (3.39 ± 0.97 L/s) patients, p = 0.003. Logistic regression results suggest that MCT outcome is inversely related to FEF25-75%, age, and gender. Specifically, as FEF25-75% percentage of predicted value increases, the log odds of a positive MCT decrease (odds ratio (OR) = 0.90, 95% confidence intervals (CI) = 0.84‐0.96, p = 0.002). Also, as age increases, the log odds of a positive MCT decrease (OR = 0.95, 95%CI = 0.94‐0.97, p < 0.001). Conclusions Reduced FEF25-75% in adults with nonobstructive spirometry can predict a positive response to MCT in younger patients. However, this relationship becomes weaker with increasing age.
Highlights
Asthma remains one of the most prevalent chronic respiratory illnesses and carries a high clinical and socioeconomic burden [1]
Mean FEF25-75% was significantly lower in methacholine challenge test (MCT) positive (3:12 ± 0:99 L/s) vs. MCT negative (3:39 ± 0:97 L/s) patients, p = 0:003
This effect was more pronounced on comparison of FEF25-75% percentage of predicted values, 88:29 ± 22:05% for MCT positive vs. 100:13 ± 22:85% for negative patients, p < 0:001
Summary
Asthma remains one of the most prevalent chronic respiratory illnesses and carries a high clinical and socioeconomic burden [1]. Airway hyperresponsiveness is a key component of bronchial asthma [3], and demonstrating its presence or absence can greatly help in establishing a diagnosis and guiding treatment. Bronchial challenge tests are commonly utilized in the secondary and tertiary care setting to look for airway hyperresponsiveness and can be performed using inhaled methacholine, histamine, and mannitol or by exercise or eucapnic hyperventilation as provocative stimulus. These tests have high sensitivity but low specificity for diagnosis of asthma [4, 5]. The methacholine challenge test (MCT) is one of the commonest tests used in clinical practice to elicit airway hyperresponsiveness and is the test we use at our institution
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