Accuracy of a Bedside Heparin Anticoagulation Monitoring Test in Critically Ill Patients

Anticoagulation therapy with unfractionated heparin (UHF) is a mandatory treatment for many critically ill patients. While the gold standard for monitoring this therapy remains the laboratory-based aPTT (aPTT-lab), the need for immediate results has led to an increase in the development of point-of-care (POC) measurement systems. This study assessed the correlation and agreement between activated clotting time-low range (ACT-LR) and aPTT-POC measurements using aPTT-lab in a cohort of critically ill patients requiring anticoagulation. This prospective cohort study involved patients admitted to the intensive care unit (ICU) who were treated with UFH between January 2022 and January 2024. We performed simultaneous measurements of aPTT-lab, aPTT-POC, and ACT-LR and analyzed 14 samples from healthy volunteers (the control group) to determine the range of normality and mean aPTT-POC. The aPTT-lab value was considered the gold standard measure of coagulation. A poor correlation was observed between ACT-LR and aPTT-lab in the global sample (r = 0.51), which improved slightly when excluding patients with invasive devices (r = 0.61). aPTT-POC showed moderate agreement (bias of 10.4%) but underestimated the aPTT ratio (bias = -0.23), which was similar in patients with and without devices. Agreement was very high in the control group (bias = -0.003). The accuracy of POC anticoagulation monitoring systems is limited in critically ill patients. The aPTT-POC measurements showed better agreement than the ACT-LR measurements. A clinical validation study is needed to adjust for systematic bias in patients with aPTT-POC.