A cutoff value for the Systemic Immune-Inflammation Index in determining activity of Behçet disease

Behçet disease (BD) is an immune-mediated vasculitis-like syndrome characterized by recurrent aphthous lesions and various systemic manifestations. Inflammatory markers may be useful to assess disease severity. The Systemic Immune-Inflammation Index (SII) (neutrophils × platelets/lymphocytes) has been widely used in oncology since 2014, with promising results.

To assess the efficiency of the SII in determining activity of BD.

This retrospective cohort study was conducted on patients with BD who were admitted to the outpatient clinic of the Department of Dermatology and Venereology, Ufuk University Hospital, between 1 January 2010 and 31 December 2019. Patients were divided into two groups based on their disease status upon admission: (i) active BD (n = 103), and (ii) inactive BD (n = 63). Clinical characteristics, demographic features, type of medications, full blood count parameters, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), ferritin and SII were compared between the groups. Furthermore, receiver operating characteristic curve analysis was performed to assess the performance of the SII in determining disease severity upon admission to hospital.

Higher numbers of white blood cells, platelets and neutrophils, greater red cell distribution width, higher levels of ESR, CRP and ferritin, and higher SII were observed in the active disease group (P < 0.001). The cutoff value of 552 × 10³ /mm³ was found to have 81% sensitivity and 82% specificity.

The SII may be used as an additional indicator for the assessment of BD status and physicians should be cautious in patients with SII levels of > 552 × 10³ /mm³ ) at the initial evaluation of the patients.