Comparison of venous and fingertip plasma using non-targeted proteomics and metabolomics

Blood tests, which are used to evaluate health status, are relatively non-invasive and provide a great deal of health-related information. Blood is usually collected using a standard venous blood sampling protocol, but it is possible to collect blood from a subject's fingertip, and previous studies have investigated whether fingertip-derived blood can be used for various blood tests. In this study, the proteomes and metabolomes of venous and fingertip plasma were analyzed using non-targeted proteomics and metabolomics, respectively. In proteomics, the levels of 523 proteins were compared between venous and fingertip plasma. The correlation coefficient (r) for the relationship between protein levels of venous and fingertip plasma was 0.9999. Some proteins had high fingertip to venous plasma level ratios (finger:venous ratios), whereas others had low finger:venous ratios, and the mean±standard deviation (SD) finger:venous ratio was 0.994 ± 0.304. In metabolomics, 40, 33, and 216 cationic metabolites, anionic metabolites, and lipids, respectively, were detected in venous plasma, and the equivalent figures for fingertip plasma were 40, 35, and 216, respectively. Regarding the correlations between metabolite levels in venous and fingertip plasma, the correlation coefficients (r) for cationic metabolites, anionic metabolites, and lipids were 0.9952, 0.9699, and 0.9980, respectively. The mean±SD finger:venous ratio was 1.19 ± 0.584 for cationic metabolites, 1.23 ± 0.548 for anionic metabolites, and 1.00 ± 0.245 for lipids. Our study suggests that it might be possible to use fingertip plasma to measure plasma protein and metabolite levels, and will contribute to development of a fingertip blood sampling procedure for measuring blood biomarker levels.