In fact, the prime attempt to quantify the proportion of enzymatically active KLK6 relative to total immunoreactive KLK6 was in 2008, by Oikonomopoulou et al.,18 who developed an ELISA using an ABP that targets trypsin-like serine proteases, coupled to a capturing antibody for KLK6, to specifically monitor the active KLK6 in CSF, ascites fluid from ovarian cancer patients, and supernatants from cancer cell lines. Here, KLK6 is linked to cancer.