In the associated main paper (“Labeled substance P as a neuropeptide reporter substance for enzyme activity” (http://doi.org/10.1016/j.jpba.2019.112953)), substance P was shown to be a valuable neuropeptide reporter substance to monitor the protease activity of serum. The assay was developed based on the predecessor assay using bradykinin (“A vote for robustness: Monitoring serum enzyme activity by thin-layer chromatography of dabsylated bradykinin products”, http://doi.org/10.1016/j.jpba.2017.06.007). Both neuropeptides are of interest in inflammation and pain research and were thus explored for use with capillary blood and blood cards (see associated MethodX paper “Neuropeptide reporter assay for serum, capillary blood and blood cards”). Here, we present validation data for the assay when sampling with blood cards as well as data on the use of fresh capillary blood.