Comparing Venous vs. Capillary Blood Collection Methods for Proteomic Measurement in Peripheral Blood

Capillary blood collection has a number of advantages over venous collection, especially in the context of increasing decentralized clinical trials and field-based testing. No studies are available comparing venous versus capillary blood collection for proteomics measurement. The aim of this study was to compare venous versus capillary blood collection methods for proteomic measurement in peripheral blood.

The expression of 368 different proteins from the Olink Explore 384 Inflammation panel was measured in both venous and capillary blood samples collected from 22 individuals at a single time point. Protein levels from venous and capillary blood samples were compared with descriptive statistics and correlation calculations. Correlations were examined for a subset of proteins identified in recent reports as associated with morbidity and mortality.

Strong positive correlation (r ≥ 0.7) between protein concentrations measured in venous and capillary blood samples was observed for two in three proteins tested (215 of 327, 66%). A further 47 (14%) showed a moderate positive correlation (0.4 ≤ r < 0.7), with weak or very weak correlation (r < 0.4) observed for the remaining 65 (20%). Protein expression was consistently higher in capillary blood samples for proteins with lower correlation (r < 0.6) between sampling methods. Further work is required to understand the underlying reasons why proteins were consistently under-expressed in venous samples/over-expressed in capillary samples in a minority of proteins tested.

Proteomic measurement utilising capillary blood collection provides very similar results to using venous blood collection. This is a promising sign for the validity and reliability of studies using capillary blood collection, including decentralised and remote studies.