CRP and pericarditis: High-sensitivity C-reactive protein (hs-CRP) can be used to predict recurrence, but it has certain limitations.<h4>Objectives</h4>This study aimed to evaluate the association between a novel biomarker, the Systemic Immune-Inflammation Index (SII), and the recurrence of acute pericarditis.<h4>Methods</h4>This retrospective cohort study included 110 patients diagnosed with acute idiopathic pericarditis, the primary endpoint of the study was to investigate Recurrent Pericarditis (RP) during the 18 month follow-up period.