The relationship of systemic immune inflammation index with subclinical inflammation in familial mediterranean fever patients

Familial Mediterranean Fever (FMF) is an autoinflammatory disease with recurrent attacks of fever and accompanying serosal membrane inflammation (pleuritis, peritonitis), arthritis, and erysipelas-like rash. Recently, studies on markers such as Neutrophil/Lymphocyte ratio (NLR) and Platelet/Lymphocyte ratio (PLR) have been conducted as indicators of subclinical inflammation. In this study, we aimed to evaluate the use of the Systemic Immune-Inflammation Index (SII=NeutrophilxPlatelet/Lymphocyte) as a subclinical inflammation marker in the follow-up of FMF patients. A total of 106 patients, 56 patients in the attack-free period and 50 healthy groups, diagnosed with FMF between 01.01.2011 and 31.12.2021, followed up in the Internal Medicine Rheumatology Outpatient Clinic of Mersin University Medical Faculty Hospital, were included in this retrospective study. Age, gender, demographic data of patients and healthy individuals, inflammation markers such as hemogram (neutrophil, lymphocyte, thrombocyte), sedimentation, C-Reactive protein (CRP) were recorded. SII measurements of FMF patients in the attack-free period and healthy group were evaluated. A statistically significant difference was found in SII values ​​between FMF patients and the healthy group (p=0.002). The discrimination power of the SII parameter on patients and controls was evaluated by Receiver Operating Curve (ROC) analysis. The success of the parameter in classification was found to be statistically significant (p=0.002). A statistically significant, linear positive and moderate correlation was found between the SII measurement taken in FMF patients and the sedimentation measurement (p=0.006; r=0.362). Our study supports the use of SII as a useful biomarker of subclinical inflammation in FMF patients. SII can be an inexpensive and easily accessible assessment tool that can assist the clinician in identifying FMF patients with active disease.