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Diagnosis of laryngotracheal stenosis during routine spirometry using the ‘Expiratory Disproportion Index’
Author(s) -
Nouraei S.A.R.,
Murphy K.,
Nouraei S.M.,
Patel A.,
Cummin A.R.,
Howard D.J.,
Sandhu G.S.
Publication year - 2008
Publication title -
clinical otolaryngology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.914
H-Index - 68
eISSN - 1749-4486
pISSN - 1749-4478
DOI - 10.1111/j.1749-4486.2008.01843_10.x
Subject(s) - medicine , spirometry , asthma , stenosis , airway , radiology , surgery
Objectives. Laryngotracheal stenosis (LTS) is an under‐recognized cause of dyspnoea and ‘wheeze’. Early treatment improves outcome while diagnostic failure leads to treatment for presumed ‘resistant’ broncho‐pulmonary pathology which increases morbidity and places the patient at ongoing risk of acute‐on‐chronic airway obstruction. The diagnostic challenge of LTS, which is an uncommon cause of a common clinical presentation lies in identifying index cases without having to subject masses of patients to unnecessary and invasive tests. We evaluated the utility of spirometry, particularly the ‘Expiratory Disproportion Index’ (EDI) in differentiating between LTS and other respiratory conditions. Methods. Diagnostic utility of EDI (FEV1/PEFR) was investigated in 9621 patients, including 3118 volunteers, 3461 patients with COPD, 1650 asthmatics, 920 patients with pulmonary fibroses, 332 patients with rare lung diseases, and 140 patients with LTS. The dataset was randomly spliced. One set was used for diagnostic rule extraction and the second for validation. Results. Area under the ROC curve for differentiating LTS from other broncho‐pulmonary diagnoses was 0.985 ± 0.011. At a threshold of 9, sensitivity of 93.4% and specificity of 96.8% were achieved. There was a significant correlation between residual tracheal cross‐section and EDI ( r = 0.61; P < 0.0001). Conclusions. EDI is a sensitive and specific spirometric test for LTS and can reliably rule in or rule out this diagnosis. It is based on PEFR‐FEV1 disproportionation, which almost exclusively occurs in patients with supra‐carinal stenosis. We recommend its use for screening defined at‐risk populations like post‐intensive‐care and Wegener's patients, and suggest more general application in evaluating patients with dyspnoea.