Inflammatory disorders, such as asthma, are associated with primed eosinophils. These primed and activated cells have an increased propensity to release ECP during in vitro clotting. Conversely, in a healthy person, the eosinophils are not primed and activated, and consequently much less ECP is released from the eosinophils during in vitro clotting. The discrimination between healthy and asthmatic patients is much more pronounced with ECP measurement in serum compared with plasma samples. In serum, the clotting factors amplify the release of ECP from eosinophils. High concentrations of in vitro released ECP reflect the eosinophilic inflammation in asthmatic patients.