To compare magnetic resonance imaging (MRI)-based and laryngoscopy-based subglottic stenosis (SGS) grading with pulmonary function testing (PFT) in patients with granulomatosis with polyangiitis (GPA).
In this retrospective study, we included 118 examinations of 44 patients with GPA and suspected SGS. All patients underwent MRI, laryngoscopy, and PFT. Stenosis was graded on a 4-point scale by endoscopy and MRI using the Meyer-Cotton (MC) score (score 1: ≤50%, 2: 51-70%, 3: 71-99%, and 4: 100%) and as percentage by MRI. Results were compared with peak expiratory flow (PEF) and maximum inspiratory flow (MIF) from PFT, serving as objective functional reference.
In MRI, 112 of 118 examinations (95%) were rated positive for SGS (grade 1 [n = 82], grade 2 [n = 26], and grade 3 [n = 4]), whereas in laryngoscopy 105 of 118 examinations (89%) were rated positive for SGS (grade 1 [n = 73], grade 2 [n = 24], and grade 3 [n = 8]). MRI and laryngoscopy agreed in 75 of 118 examinations (64%). MRI determined higher scores in 20 examinations (17%) and lower scores in 23 examinations (19%) compared to laryngoscopy. MC scores as determined by both MRI and laryngoscopy showed comparable correlations with PEF (r = -0.363, P = 0.016, and r = -0.376, P = 0.012, respectively) and MIF (r = -0.340, P = 0.024, and r = -0.320, P = 0.034, respectively). The highest correlation was found between MRI-based stenosis grading in percentage with PEF (r = -0.441, P = 0.003) and MIF (r = -0.413, P = 0.005).
MRI and laryngoscopy provide comparable results for grading of SGS in GPA and correlate well with PFT. MRI is an attractive noninvasive and radiation-free alternative for monitoring the severity of SGS in patients with GPA.