Objective:

To investigate the association between serum IQGAP3 levels and coronary lesion severity, and to evaluate the diagnostic value of combining IQGAP3 with the triglyceride glucose-body mass index (TyG-BMI) in patients with type 2 diabetes mellitus (T2DM).

Approach:

• Study Design: Prospective study enrolling T2DM patients undergoing coronary angiography.
• Measurements: Serum IQGAP3 levels measured by enzyme-linked immunosorbent assay; TyG-BMI calculated using routine clinical parameters.
• Assessment of Coronary Lesion Severity: Coronary lesion severity assessed using the Gensini score and categorized by tertiles.
• Statistical Analysis: Multivariable logistic regression, restricted cubic spline analyses, ROC curves, NRI, and IDI used to assess model performance.

Key Findings:

• Serum IQGAP3 levels and TyG-BMI significantly increased across Gensini score tertiles (P< 0.05).
• Both IQGAP3 (OR = 3.119, 95% CI: 2.049–4.747, P< 0.001) and TyG-BMI (OR = 1.012, 95% CI: 1.003–1.021, P = 0.006) were independently associated with severe coronary stenosis.
• Adding TyG-BMI to traditional risk factors improved discrimination (AUC: 0.702 vs. 0.753; P< 0.001).
• Incorporating IQGAP3 further increased AUC to 0.803 and improved reclassification (NRI = 0.307, IDI = 0.138; P< 0.001).
• Age modified the association between IQGAP3 and severe coronary stenosis (Pinteraction = 0.036), with stronger effects in patients younger than 65 years.

Interpretation:

Limitations:

• The study is limited to a single center and may not be generalizable to all populations.
• The observational design limits causal inferences.

Conclusion: