Utility of Routine Spirometry Measures for Surveillance of Idiopathic Subglottic Stenosis.

Importance: Because of the recurrent nature of idiopathic subglottic stenosis, routine follow-up is necessary for monitoring progression of stenosis. However, no easily accessible, standardized objective measure exists to monitor disease progression.
Objective: To determine whether peak expiratory flow (PEF) can be used as a reliable and easily accessible biometric indicator of disease progression relative to other validated spirometry measures in patients with idiopathic subglottic stenosis.
Design, Setting, and Participants: Prospectively collected data on PEF, expiratory disproportion index (EDI), and total peak flow (TPF) from 42 women with idiopathic subglottic stenosis without comorbid lower airway or parenchymal lung disease who were treated at a single tertiary referral center between 2014 and 2018 were analyzed. The mean follow-up period was 18.2 months (range, 2-40 months). Ten patients initially screened were not included in the analysis owing to comorbid glottic or supraglottic stenosis or nonidiopathic etiology.
Main Outcomes and Measures: Measurements of PEF, EDI, and TPF were taken at preoperative visits and at all other visits.
Results: Forty-two women (mean age, 51.5 years; 98% white [n = 41]) met the inclusion criteria. The area under the curve for PEF was 0.855 (95% CI, 0.784-0.926). The optimal cutoff value was 4.4 liters per second (264 L/min), with a sensitivity and specificity of 84.4% and 82.0%, respectively. The area under the curve for EDI was 0.853 (95% CI, 0.782-0.925). For TPF, this was 0.836 (95% CI, 0.757-0.916).
Conclusions and Relevance: This study provides evidence supporting the use of PEF as a simple, efficient, and accessible way of monitoring progression of idiopathic subglottic stenosis and predicting receipt of surgical intervention. Sensitivity and specificity of PEF were comparable to those of the more complex measures of TPF and EDI.