A Novel Laboratory Assay to Monitor Unfractionated Heparin Dosing in Patients Taking Apixaban Prior to Hospital Admission.

Introduction: When monitoring heparin, anti-Xa assays are susceptible to interference from apixaban taken before admission and can result in inappropriate dose adjustments that can negatively affect patient care.

Methods: We derived a novel assay, termed corrected heparin (CH), using quantified values from a chromogenic anti-Xa assay with heparin calibrators before and after heparinase treatment to eliminate any interference from apixaban within the patient sample. We retrospectively assessed 469 specimens from 72 patients at our institution who had their unfractionated heparin infusion monitored using the CH assay because of known apixaban use.