Proof-of-concept experiment for functional protease profiling with reporter peptide spiking. Serum specimens were spiked with CP-RP and IS and incubated for 22 h as described in materials and methods. (A) CP-AP concentrations in serum specimens of healthy controls (HC), inflammatory controls (IC) and tumor patients (TP). In the box plot the central box represents the values from the lower to upper quartile (25 to 75 percentile). The middle line represents the median. The horizontal line extends from the minimum to the maximum value. P-values of the Mann–Whitney test are indicated. (B) ROC-AUC calculation for separation of tumor patients (TP) from healthy controls (HC) (left graph), tumor patients (TP) from inflammatory controls (IC) (middle graph) and healthy controls from inflammatory controls (IC) (right graph).