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

Anticoagulation therapy with unfractionated heparin (UHF) is a mandatory treatment for a large group of critically ill patients. Although the gold standard for its monitoring is still the laboratory aPTT (aPTT-lab), the need for inmediate results has led to an increase in the number of point of care (POC) measurement systems. The objective of this study was to assess the correlation and agreement between activated Clotting Time- Low Range (ACT-LR) and aPTT-POC measurements with aPTT-lab in a cohort of critically ill patients requiring anticoagulation. This prospective cohort study included patients admitted to the intensive care unit (ICU) treated with UFH between January 2022 and January 2024. Simultaneous measurements of aPTT-lab, aPTT-POC, and ACT-LR were performed. To determine the range of normality and mean aPTT-POC, we analyzed 14 samples fromMhealthy volunteers who represented the control group. The aPTT-lab value was considered the gold standard. We found a poor correlation in the global sample between ACT-LR and aPTT-lab (r= 0,51), improving slightly after excluding patients with invasive devices (r= 0,61). aPTT-POC showed moderate agreement (bias of 10.4%), underestimating the aPTT ratio (bias= -0.23), which was similar in patients with and without devices. In the control group of healthy volunteers, agreement was very high (bias=-0.003). The accuracy of a POC anticoagulation monitoring system in critically ill patients is limited. The aPTT-POC measurements showed better agreement than the ACT-LR measure-ments. A clinical validation study is needed to adjust for systematic bias in patients with aPTT-POC.