Agreement between fingertip-capillary and antecubital-venous appetite-related peptides

This study examined the agreement between fingertip-capillary and antecubital-venous measures of appetite-related peptides. Simultaneous fingertip-capillary and antecubital-venous blood samples were collected from 19 participants. The samples were obtained at baseline, 30, 60, 90, and 120 min following breakfast for the determination of plasma GLP1_7-36, glucagon, insulin and leptin. Between-day reproducibility of fingertip-capillary-derived estimates was assessed in 18 participants. Deming regression, limits of agreement (LOA) and typical error as a coefficient of variation (CV) were used to quantify agreement (CV_a) and reproducibility (CV_r). Deming regression revealed no systematic bias for any of the analytes studied, but for insulin there was evidence of a proportional difference at higher concentrations. Measures of GLP1_7-36 (CV_a=24.0%, LOA ±2.5 pg m/l per h), leptin (CV_a=9.0%, LOA ×/÷1.19) and glucagon (CV_a=21.0%, LOA, ±31.5 pg m/l per h) revealed good agreement between methodological approaches. Fingertip-capillary glucagon was highly reproducible between days (CV_r=8.2%). GLP1_7-36 and leptin demonstrated modest reproducibility (CV_r=22.7 and 25.0% respectively). For insulin, agreement (CV_a=36.0%, LOA ×/÷1.79) and reproducibility were poor (CV_r=36.0%). Collectively, the data demonstrate that fingertip-capillary blood sampling provides a comparable and reproducible alternative to antecubital-venous blood sampling for the quantification of glucagon, and to a lesser extent for GLP1_7-36 and leptin. Caution should be exercised when utilising fingertip-capillary blood sampling for insulin quantification, and consequently should not be employed interchangeably with antecubital-venous blood sampling.