PCSK9 and diabetes mellitus: Further, multivariate Cox regression analysis based on the combination of PCSK9 levels and DM status revealed that only the subgroup with DM plus high PCSK9 levels had a significantly higher risk of MACEs compared with the reference subgroup (non-DM plus low PCSK9 levels) (HR: 1.996, 95% CI 1.047–3.817, P = 0.036) (Additional file 2: Table S2).