Evaluation of measured and calculated small dense low-density lipoprotein in capillary blood and association with the metabolic syndrome

•Directly measured and estimated sdLDL-C concentrations are comparable between capillary and venous blood.•sdLDL-C in capillary blood is stable for 24 h at RT.•There is a bias of calculated and directly measured sdLDL-C compared with the electrophoretic method.•Directly measured and estimated sdLDL-C are increased in the MS and associate with vascular damage. Small-dense-low-density-lipoprotein cholesterol (sdLDL-C) is proatherogenic and not commonly measured. The aims were to evaluate capillary blood and its stability for sdLDL-C measurement and measure sdLDL-C in patients with metabolic syndrome (MS). 182 patients were studied (49 with MS). sdLDL-C was measured by electrophoresis (LipoPrint®), direct measurement (Roche Diagnostics) and Sampson equation. Intima-media thickness (IMT) and presence of atheroma was evaluated. sdLDL-C was compared in paired venous and capillary blood according to CLSI-EP09c (n = 40). sdLDL-C stability was studied after 24 h at room temperature (RT). sdLDL-C in capillary blood and venous blood showed agreement with the direct measurement (bias: 4.17 mg/dL, LOA 95 %:−5.66; 13.99) and estimation (bias:8.12 mg/dL, LOA 95 %:−8.59; 24.82). sdLDL-C is stable in capillary blood for 24 h at RT. The electrophoretic method yielded lower (p