C‐Reactive Protein Serum Values in Idiopathic and Autoimmune Subglottic Stenosis

ABSTRACT Objective (s) Idiopathic and granulomatosis with polyangiitis (GPA)‐related subglottic stenosis (SGS) are considered distinct immune‐mediated inflammatory disorders. Limited data exist on serum inflammatory markers, specifically C‐Reactive Protein (CRP), for SGS diagnosis, differentiation, and prognostication. The study objective was the characterization of CRP levels in idiopathic (iSGS) and GPA‐SGS to assess CRP's ability to distinguish SGS subtypes and predict SGS progression and recurrence. Methods Retrospective review of patients with idiopathic or GPA‐SGS from 2007 to 2024 at a single institution. Surgery‐free interval (SFI) was calculated as the time between surgical interventions. Statistical analysis included independent t‐tests, chi‐squared, and univariate linear regression. Results 59 iSGS and 47 GPA‐SGS patients were included. CRP was elevated in 36% of iSGS and 49% of GPA‐SGS patients (0.0.6 mg/dL). Mean maximum CRP was 2.7 mg/dL lower in iSGS compared to anti‐neutrophil cytoplasmic antibody (ANCA)‐positive GPA‐SGS ( p = 0.035). The maximum CRP in iSGS was 3.6 mg/dL, while 10 (21%) GPA patients had CRPs greater than 3.6 mg/dL (max = 31 mg/dL). ANCA‐negative GPA‐SGS mean CRP was not significantly different than iSGS or ANCA‐positive GPA‐SGS. CRP and SFI did not correlate on univariate linear analysis. Conclusion Mild elevation of CRP is common in SGS patients. High CRP levels are more frequent in GPA‐SGS, potentially aiding clinical differentiation of etiologies. However, CRP at presentation does not appear to correlate with disease recurrence in iSGS or GPA‐related SGS, limiting its value as a biomarker and prognostic tool. Level of Evidence 3