title: Physiology-based minimum clinically important difference thresholds in adult laryngotracheal stenosis.
abstract: OBJECTIVE
  Delivering evidence-based patient care is predicated on the availability of objective and validated outcome measures. We aimed to calculate physiology-based minimum clinically important difference (MCID) values for adult laryngotracheal stenosis (LTS).
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Patient demographics, morbidities, and stenosis severity were assessed preoperatively. Flow-volume loops and Medical Research Council (MRC) dyspnea grades were measured in 21 males and 44 females before and 6 to 8 weeks after airway surgery, and before treating recurrent disease in 10 patients. Anchor and distribution-based methodologies were used to calculate MCIDs for treatment efficacy and disease recurrence respectively.
  
  
  RESULTS
  The mean age at treatment was 46 ± 16 years. The most common etiology was idiopathic subglottic stenosis (38%). Most lesions (66%) obstructed >70% of the lumen. There were strong correlations between treatment-related changes in total peak flow (TPF) (ΔTPF) (peak expiratory flow + |peak inspiratory flow|) and the ratio of area under the flow-volume loop (AUC) to forced vital capacity (FVC) (ΔAUCTotal /FVC), and treatment-related changes in the MRC grade (ΔMRC) (r = -0.76 and r = -0.82, respectively). Both TPF and AUCTotal /FVC discriminated between effective (ΔMRC <0) and ineffective (ΔMRC ≥0) interventions, yielding MCID values of 4.2 L/s for TPF and 2.1 L(2) /s for AUCTotal /FVC, respectively. Ten patients required airway treatment for recurrent disease, and TPF and AUCTotal /FVC levels had distribution-based MCID values of 0.9 and 0.6, respectively.
  
  
  CONCLUSIONS
  Flow-volume loops provide a quantitative method of objectively assessing outcomes in LTS. TPF is the most convenient index for this purpose, but AUCTotal /FVC provides marginally greater sensitivity and specificity.
authors.affiliation: Department of Cardiothoracic Surgery, University of Mazandaran School of Medical Sciencs, Sari, Iran.
authors.forename: S Mahmoud
authors.initials: SM
authors.lastname: Nouraei
authors.forename: Ramon A
authors.initials: RA
authors.lastname: Franco
authors.forename: Jayme R
authors.initials: JR
authors.lastname: Dowdall
authors.forename: S A Reza
authors.initials: SA
authors.lastname: Nouraei
authors.forename: Heide
authors.initials: H
authors.lastname: Mills
authors.forename: Jag S
authors.initials: JS
authors.lastname: Virk
authors.forename: Guri S
authors.initials: GS
authors.lastname: Sandhu
authors.forename: Mike
authors.initials: M
authors.lastname: Polkey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000403:Airway Resistance / Q000502:physiology*; D004724:Endoscopy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007829:Laryngostenosis / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology*; D057234:Preoperative Period; D011446:Prospective Studies; D019651:Plastic Surgery Procedures / Q000379:methods*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014135:Tracheal Stenosis / Q000175:diagnosis / Q000503:physiopathology*; D016896:Treatment Outcome; D014797:Vital Capacity / Q000502:physiology*; D055815:Young Adult
keywords: Laryngotracheal stenosis; evidence-based medicine; flow-volume loops; minimum clinically important difference; outcome measures; pulmonary function test