Increased plasma levels of APC like those observed here (1.23 pmol/L in SVT MPN+) have been reported previously in thrombophilic patients that carried the FV Leiden mutation (1.30 pmol/L [27] or the prothrombin 20210G>A mutation (1.03 pmol/L [28]). Here, F5 is linked to myeloproliferative neoplasm.