Combined diagnostic value of the systemic immune-inflammation index and LDL for coronary microvascular disease: a retrospective cohort study

BACKGROUND: of major adverse cardiovascular events. The diagnosis of CMVD relies on coronary function testing or noninvasive imaging techniques, which are not universally available and may limit routine clinical implementation. OBJECTIVES: Growing evidence supports the notion that biological processes such as inflammation and oxidative stress drive vascular aging and contribute to microvascular dysfunction. The systemic immune-inflammation index (SII) is a marker used to assess immune-inflammatory and thrombotic status and has shown prognostic value in chronic heart failure, and acute myocardial infarction. However, its role in CMVD remains underexplored. DESIGN: To address this gap, we retrospectively analyzed 180 patients with angina who underwent myocardial contrast stress echocardiography between January and November 2022 at the First Affiliated Hospital of Harbin Medical University. METHODS: Based on coronary microcirculatory function, patients were divided into two groups: 91 with normal function and 89 with microcirculatory disorders. Clinical data and lab indicators were compared. Logistic regression identified SII, LDL cholesterol as independent CMVD predictors. Pearson correlation demonstrated an inverse relationship between SII and coronary flow reserve, supporting its link with impaired microvascular function. Receiver operating characteristic analysis further showed that the combined SII and LDL model provided improved discriminatory performance compared with either marker alone, achieving an area under the curve of 0.76 with a sensitivity of 77.5% and specificity of 69.2%. CONCLUSION: SII is independently associated with CMVD and improved discriminatory performance when combined with LDL.