Although P5 (preventive, personalized, predictive, participatory, psychocognitive) medicine and patient-focused healthcare are gaining ground in various healthcare areas, the diagnosis of antithrombin deficiency (ATD) is still based on crude diagnostic tests, clustering patients into clinically heterogeneous subgroups whereby relevant thrombophilia phenotypes may go unnoticed. […] Plasma from 91 unrelated ATD patients and 41 patients with a congenital disorder of glycosylation affecting antithrombin glycosylation were characterized functionally, genetically, and analyzed by LC-MRM-MS.