title: Use of chromogenic assay of factor X to accept or reject INR results in Warfarin treated patients.
abstract: A warfarin treated patient unexpectedly presented with an elevated international normalized ratio (INR). Repeat testing in two laboratories gave conflicting results. The chromogenic assay of factor X was used to determine the correct INR result. The patient had laboratory results consistent with a dysfibrinogenemia, which prevented detection of the endpoint with a photo-optical detection system. The chromogenic assay of factor X is recommended for monitoring patients on warfarin when the INR cannot be accurately determined due to interference with the fibrin endpoint in the INR.
authors.affiliation: Coagulation Services, Marshfield Labs, Marshfield Clinic, 1000 North Oak Avenue, Marshfield, WI 54449, USA. sanfelippo.michael@marshfieldclinic.org
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sanfelippo
authors.forename: Wendy
authors.initials: W
authors.lastname: Zinsmaster
authors.forename: Doris L
authors.initials: DL
authors.lastname: Scherr
authors.forename: Gene R
authors.initials: GR
authors.lastname: Shaw
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects; D002863:Chromogenic Compounds; D005170:Factor X / Q000378:metabolism*; D005260:Female; D005337:Fibrin / Q000737:chemistry*; D005340:Fibrinogen / Q000276:immunology; D006333:Heart Failure / Q000150:complications; D006801:Humans; D019934:International Normalized Ratio; D008175:Lung Neoplasms / Q000150:complications / Q000601:surgery; D011517:Prothrombin Time; D013997:Time Factors; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D002863:Chromogenic Compounds; D014859:Warfarin; D005170:Factor X; D005337:Fibrin; D005340:Fibrinogen