Metabolic syndrome (MetS) is a global health concern characterized by a cluster of metabolic abnormalities, including central obesity, hypertension, hyperglycemia, and dyslipidemia, which increase the risk of cardiovascular disease and type 2 diabetes. This systematic review and meta-analysis aimed to assess the diagnostic value of salivary C-reactive protein (CRP) as a non-invasive biomarker for MetS. A comprehensive search of PubMed, Cochrane Library, and Web of Science was conducted through December 2024. Eligible studies reported salivary CRP levels in individuals with and without MetS. Two independent reviewers extracted data on study design, demographics, CRP measurement methods, and diagnostic criteria for MetS. Meta-analyses were performed using random-effects models to calculate pooled standardized mean differences (SMDs) with 95% confidence intervals. Among 863 records screened, 19 studies involving 3,157 participants met the inclusion criteria. The pooled results showed significantly higher salivary CRP levels in individuals with MetS compared to controls (Hedges’ g = 1.02; 95% CI: | 0.23, 1.81] P = 0.01). High between-study heterogeneity was observed (I² = 98.91%, P < 0.001), and funnel plot asymmetry suggested potential publication bias or underlying heterogeneity. These findings suggest that salivary CRP may serve as a promising non-invasive biomarker for detecting metabolic syndrome.

Metabolic syndrome (MetS) is a cluster of conditions that rely on low-grade systemic inflammation and increase the risk of cardiovascular disease, type 2 diabetes, and stroke. C-reactive protein (CRP) has attracted growing interest in saliva as a non-invasive alternative to serum CRP testing, though existing evidence remains inconsistent. This systematic review and meta-analysis evaluated the association between salivary CRP levels and MetS and examined the consistency of findings across populations and methodological approaches. PubMed, the Cochrane Library, and Web of Science were searched up to December 2024 following PRISMA 2020 guidelines. Nineteen studies involving 3265 participants with and without MetS were included. Random-effects meta-analysis demonstrated higher salivary CRP levels in individuals with MetS compared with controls (SMD = 1.02; 95% CI −0.23 to 1.81), with substantial heterogeneity (I² = 98.91%), reflecting variation in population characteristics and saliva collection protocols. Funnel plot assessment did not indicate publication bias. Despite considerable heterogeneity, pooled estimates suggest that individuals with MetS have higher levels of salivary CRP. Longitudinal studies employing standardized methodologies are required before its clinical implementation can be considered.