The role of systemic immune-inflammation index (SII) in the differential diagnosis of granulomatous and reactive LAP diagnosed by endobronchial ultrasonography

BACKGROUND AND AIM: Tuberculosis and sarcoidosis are the two most important granulomatous diseases that physicians have difficulty differentiating. In our study, we aimed to observe the utility of systemic immune-inflammation index (SII) in the differentiation of patients diagnosed by endobronchial ultrasound (EBUS)-guided lymph node biopsy. METHODS: Our study included 494 patients who presented to the chest diseases outpatient clinic of our hospital between 2015 and 2020 and underwent EBUS-guided biopsy for mediastinal lymphadenopathy (LAP). The patients’ pre-procedural hematologic parameters and results of at least 2-year follow-up after diagnosis were retrospectively evaluated. RESULTS: When compared by patient group, SII was significantly higher in patients with tuberculous lymphadenitis compared to those with sarcoidosis and reactive LAP (p=0.01 and <0.001, respectively) and in patients with sarcoidosis compared to those with reactive LAP (p=0.002). Among patients with sarcoidosis, platelet count, erythrocyte sedimentation rate, and SII were significantly higher in stage 2 patients compared to stage 1 patients, while lymphocyte levels were lower (p=0.009, 0.001, 0.001, and 0.001 respectively). In the ROC curve analysis of SII between patients with sarcoidosis and tuberculosis LAP, the area under the curve was 0.668. At a cut-off value of 890.7, SII had 70% sensitivity and 66% specificity in the differentiation of tuberculosis and sarcoidosis lymphadenitis. CONCLUSION: SII is an easily obtained parameter that may aid in the differentiation of tuberculosis and sarcoidosis LAP with granuloma and in the differentiation of granulomatous diseases from reactive LAP.