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

Background: The present study examined the agreement between fingertip-capillary and antecubital-venous measures of appetite-related peptides. Methods: Simultaneous fingertip-capillary and antecubital-venous blood samples were collected from 19 participants. Samples were obtained at baseline, 30, 60, 90 and 120 min following breakfast consumption for determination of plasma GLP-17-36, 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 (CVa) and reproducibility (CVr). Results: 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 GLP-17-36 [CVa = 24.0%, LOA ± 2.5 pg•mL-1•h-1], leptin (CVa = 9.0%, LOA ×/÷ 1.19) and glucagon [CVa = 21.0%, LOA, ± 31.5 pg•mL-1•h-1] revealed good agreement between methodological approaches. Fingertip-capillary glucagon was highly reproducible between days (CVr = 8.2%). GLP-17-36 and leptin demonstrated modest reproducibility (CVr = 22.7 and 25.0%, respectively). For insulin, agreement (CVa = 36.0%, LOA ×/÷ 1.79) and reproducibility was poor (CVr = 36.0%). Conclusion: Collectively, the data demonstrate fingertip-capillary blood provides a comparable and reproducible alternative to antecubital-venous blood sampling for quantification of glucagon, and to a lesser extent for GLP-17-36 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.