Subjective assessment using still bronchoscopic images misclassifies airway narrowing in laryngotracheal stenosis

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Abstract
Severity of airway narrowing is relevant to management decision-making processes in patients with laryngotracheal stenosis. Airway lumen is frequently assessed subjectively based on still images obtained during airway examinations or objectively using image analysis software applied to radiological or bronchoscopic images. The purpose of this study was to determine whether strictures classified as mild, moderate or severe degrees of airway narrowing based on subjective assessments by a group of experienced bronchoscopists using still images, matched the classifications derived from morphometric bronchoscopy measurements and whether the results of subjective assessments correlated with the level of bronchoscopic experience. Thirty-five bronchoscopic doublet still images of benign causes of laryngotracheal stenosis containing normal and abnormal airway cross-sectional areas were objectively analysed using morphometric bronchoscopy and classified as mild (70%). These images were then subjectively assessed by 42 experienced bronchoscopists participating in an interventional bronchoscopy course. Descriptive statistics were used to explore the accuracy of the participants’ classifications. Correlation coefficients were used to study the relationship between participants’ subjective assessments and bronchoscopy experience. Only 47% of strictures were correctly classified by study participants (mean 16.48 ± 2.8). Of the 1447 responses included in this analysis, 755 were incorrect: 71 (9%) were over-classifications of strictures’ severity and 684 (91%) were under-classifications. There was no correlation between number of strictures correctly classified and number of lifetime bronchoscopies or number of strictures seen by bronchoscopists in an average month. Experienced bronchoscopists often misclassify the degree of airway narrowing when using still bronchoscopic images to subjectively assess strictures of benign aetiology.