PB1138 - The impact of switching from Anti-Factor Xa (anti-Xa) assays to APTT to monitor intravenous (IV) unfractionated heparin (UFH) at a quaternary care academic centre.

Tuesday, June 27, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Fei fang, PhD, MD

Resident
Department of Medicine, University Health Network
Halifax, Nova Scotia, Canada

Co-Author(s)

JA

Jameel Abdulrehman

Assistant Professor
Department of Medicine, University Health Network
Toronto, Ontario, Canada
BH

Bassem Hamandi

Drug Information Pharmacist
Department of Pharmacy, University Health Network
Toronto, Ontario, Canada
Carolyne Elbaz, MDCM FRCPC MScCH

Associate Member, Oncology
Department of Medicine, McGill University
Montreal, Quebec, Canada
JV

Jason Volling

Pharmacist
Department of Pharmacy, University Health Network
Toronto, Ontario, Canada
LT

Lori Taylor

Manager, Senior Professional Practice Leader
Dept. of Collaborative Academic Practice (Nursing & Health Professions), University Health Network
Toronto, Ontario, Canada
Rita Selby, MBBS FRCPC MSc (she/her/hers)

Associate Professor
University of Toronto
Toronto, Ontario, Canada

Background: Large observational studies do not support clinical superiority of anti-Xa assays over activated partial thromboplastin time (APTT) for monitoring IV UFH. Compared to anti-Xa testing, APTT is readily available and inexpensive but may be affected by underlying coagulopathies.

Aims: To assess the impact of switching from anti-Xa to APTT for UFH monitoring on anticoagulation efficacy and cost.

Methods: The switch from routine anti-Xa to APTT monitoring for IV UFH occurred on March 1, 2018. A retrospective chart review of individual episodes of IV heparinization during the 1-year period before and after was conducted comparing total number of tests during each heparinization episode, time-to, and time-in therapeutic range (TTR) and costs associated with each monitoring method. Unique IV heparinization episodes were identified by cross-referencing laboratory and pharmacy databases. Patient demographics, IV UFH nomogram dosing (low vs. standard target), UFH infusion start and stop times, total number of anti-Xa and APTT tests, test results and costing data were collected.

Results: Table 1 includes number of episodes, number excluded, age, sex, location and length of hospital stay per group. Figure 1 details test frequency, TTR, and cost of testing between groups. Time-to-therapeutic range was significantly lower using APTT monitoring, with the same total number of tests used per group. TTR was low for both anti-Xa and APTT groups with no significant difference (38.29% vs. 37.40% respectively; p=0.24). APTT use resulted in a greater number of sub-therapeutic episodes while anti-Xa use resulted in a greater number of supra-therapeutic episodes. Total laboratory costs were significantly lower using APTT vs. anti-Xa monitoring.

Conclusion(s): Routine monitoring of IV UFH using APTT instead of anti-Xa did not result in a change in TTR but was associated with significantly lower costs. Further analysis examining various dosing and process of care predictors of TTR is ongoing.