A-329 Preliminary Clinical Method Comparison of a Near-Patient Platform for Low Blood Volume Testing of aFXa in Pediatric Patients on Heparin Therapy

Abstract

Abstract Background Up to 15% of hospitalized children receive heparin therapy and require frequent monitoring for Anti-Factor Xa activity (aFXa) and activated partial thromboplastin time (aPTT) to achieve hemostatic balance. Current heparin tests require large blood volumes, which can lead to iatrogenic anemia with frequent sample collection. We performed a small clinical method comparison of a rapid, near-patient platform for simultaneous whole blood testing of aFXa from 50 μL of sample against the clinical standard test. The aPTT assay is in development on the same digital microfluidic (DMF) platform. Methods Four DMF instruments were placed in our laboratory. Preliminary precision of the DMF aFXa assay was obtained using commercial controls (n = 19 for aFXa at 0.98 U/mL; n = 20 for aFXa at 0.42 U/mL). We obtained whole blood or plasma from residual aFXa samples from pediatric patients. Venous samples were collected from patients for routine testing in the core laboratory, and 150 μL of whole blood was saved for aFXa method comparison testing. Patients were either on low molecular weight heparin or unfractionated heparin. We performed a method comparison study to determine assay equivalence to in-house clinical standard tests using plasma for aFXa on the Stago STA R MAX to both plasma and whole blood on the DMF platform. Results For precision, we observed an assay coefficient of variation (CV) of 4.68% and 6.6% for aFXa at 0.98 U/mL and 0.42 U/mL, respectively. The aFXa assay correlated well (R2 = 0.94 for whole blood (n = 9) and R2 = 0.97 for plasma (n = 10)); additional studies are needed to demonstrate aPTT assay equivalence. Conclusions We demonstrated good correlation of the DMF aFXa assay to the clinical standard test. The low blood volume requirement make these tests suitable for use in heparin monitoring where frequent testing is necessary. A large scale clinical method comparison is planned to ensure clinical utility.