Category: Professional Posters
Purpose: Determine if the Coagsense point-of-care (POC) instrument, using mechanical clot detection, provides more reliable INR measurements than the Coagucheck XS POC instrument, using electrochemical pulse for clot detection, in comparison to a venous blood sample on the Stago benchtop instrument. Seven groups of patients were studied to evaluate if certain medical conditions may be responsible for POC INR measurement variability.
Methods: The institutional review board approved this prospective observational study at a single-center outpatient anticoagulation clinic during a single patient visit. Male (n=39) and female (n=38) patients at least 18 years old were invited to participate in the study if they had a history of Antiphospholipid Syndrome-APS (n=11), Hypercoagulable disorder (n=13), Autoimmune condition (n=10), Peripheral Vascular Disease-PVD (n=10), Mechanical Heart Valve-MHV (n=12), Atrial Fibrillation (n=11) or DVT/PE/CVA history (n=10). Consent was obtained from each patient. If their standard of care INR was 2.0 to 5.0, a total of two capillary fingerstick blood samples were drawn for the Coagsense and Coagucheck XS POC meters, and a venous citrated blood sample was drawn for the Stago laboratory instrument. The primary objective was to measure the difference in INR values between each POC instrument and the reference laboratory instrument. A secondary objective was to determine if any of the seven disease states led to higher INR differences between POC and lab analyzer, to determine if there is a subset of patients that should not be monitored by POC devices.
Results: Of the 77 patients enrolled, Coagsense correlated well (92% of INRs within 20% of Stago INR, 64% of INRs within 0.2 of Stago INR, overall INR bias of 0.1 or 4% bias). Six patients had INR readings outside the 20% allowed bias in the following groups: APS (n=2), Autoimmune (n=2), PVD (n=1) and Hypercoagulable Disorder (n=1) and could have led to incorrect warfarin dosing in 4 patients.
In comparison, Coagucheck XS INRs correlated poorly (49% within 20% of Stago INR, 10% of INRs were within 0.2 of Stago INR, overall INR bias of 0.66 or 25.7% bias). Forty-one patients had INR readings outside the 20% allowed bias in the following groups: APS (n=6), Autoimmune (n=6), PVD (n=6), Hypercoagulable Disorder (n=11), MHV (n=6), Atrial fibrillation (n=3), DVT/PE/Stroke (n=3) and could have led to incorrect warfarin dosing in 28 patients.
Coagucheck XS is known to have higher INR bias for INRs over 3.0. The Coagsense INR bias remained stable (within 0.1-0.25 INR) across all Stago INR ranges from 1.8-5.0. Coagucheck XS INR bias increased with each 0.5 increase in Stago INR. The Coagucheck XS INR to Stago INR bias (0.46-1.3 INR) was statistically significant across all INR ranges above 2.0.
Conclusion: Coagsense correlated well while Coagucheck XS INR measurements were considerably higher than Stago INR with over half of all Coagucheck XS INRs outside the 20% acceptable limit. Four disease states (Antiphospholipid Syndrome, Autoimmune, Peripheral Vascular Disease and Hypercoagulable Disorder) had higher INR variability in both POC meters; suggesting POC INR results should be correlated with venous lab INR in patients with those disease states before trusting a POC meter for warfarin dosing. Three patients correlated well on Coagucheck XS but poorly on Coagsense showing patient correlations from one POC device cannot be extrapolated to another POC device.