Q: How frequent anti-Xa and aPTT levels co-relate in managment of unfractionated Heparin (UH)?

Answer: Only 50% of time

PTT and Anti-Xa are two methods to follow threapeutic level of  Unfractionated Heparin (UH). Unfortunately, most studies have shown large discordance in their co-relation.

• Supratherapeutic APTT values but therapeutic anti-Xa results had decreased factor II activity.
• Subtherapeutic APTT but therapeutic anti-Xa values had high factor VIII activity.

References:

1. Takemoto CM, Streiff MB, Shermock KM, Kraus PS, Chen J, Jani J, Kickler T. -Activated partial thromboplastin time and anti-xa measurements in heparin monitoring: biochemical basis for discordance.- Am J Clin Pathol. 2013 Apr;139(4):450-6.

2. Elizabeth A Price MD MPH, Jing Jin MD, Huong (Marie) Nguyen MD: Gomathi Krishnan PhD, Raffick Bowen PhD, James L Zehnder MD - Discordant aPTT and Anti-Xa Values and Outcomes in Hospitalized Patients Treated With Intravenous Unfractionated Heparin - The Annals of Pharmacotherapy. 2013;47(2):151-158.