The interference of LA with reagents in POC devices is thought to be dependent on the type of thromboplastins used

The interference of LA with reagents in POC devices is thought to be dependent on the type of thromboplastins used. correlation coefficient, and BlandCAltman plots. Agreement limits were considered satisfactory if differences were 20% as determined by the Clinical and Laboratory Standards Institute. Results We found poor agreement between POCT-INR and laboratory-INR based on Lins concordance correlation coefficient (c) of 0.42 (95% CI, 0.26-0.55) between POCT-INR and Owren-INR, a c of 0.64 (95% CI, 0.47-0.76) between POCT-INR and Quick-INR, and a c of 0.77 (95% CI, 0.64-0.85) between Quick-INR and Owren-INR. High anti-2-glycoprotein I IgG antibody titers correlated with INR disagreement between POCT-INR and laboratory-INR. Conclusion There is a disagreement between INR values ML-098 measured with the CoaguChek XS and laboratory-INR in a proportion of patients with LA. Consequently, laboratory-INR monitoring should be preferred over POCT-INR monitoring in patients with LA-positive APS, especially in patients with high anti-2-glycoprotein IgG antibody titers. KeyWords: anticoagulants, international normalized ratio, lupus coagulation inhibitor, point-of-care testing, warfarin Essentials ? Lupus anticoagulant can interfere with international normalized ratio (INR) results in point-of-care testing (POCT) ? We compared 1 POCT-INR ML-098 with 2 laboratory INR tests in patients with antiphospholipid syndrome ? We found large disagreement between POCT-INR and laboratory INR ? AntiC2-glycoprotein I immunoglobulin G antibody titers correlated with INR disagreement 1.?Introduction Antiphospholipid syndrome (APS) is a rare autoimmune disease that is defined as recurrent thrombosis or pregnancy-related complications in combination with the persistent presence of antiphospholipid antibodies [1, 2, 3]. Antiphospholipid antibodies are a heterogeneous but overlapping group of autoantibodies, which include anti-2-glycoprotein I (2GPI) and anticardiolipin antibodies, and antibodies that prolong the plasma clotting time in laboratory tests in a phospholipid-dependent manner, a phenomenon known as lupus anticoagulant (LA) [4]. Considering that antiphospholipid antibodies induce a procoagulant status, the standard treatment for thrombotic APS is anticoagulation for an unspecified duration. Vitamin K antagonists (VKAs) are commonly used for secondary prophylaxis [5]. Because the use of VKAs imposes considerable bleeding risks, it requires strict monitoring using the international normalized ratio (INR) [6,7]. The optimal therapeutic window for VKAs is an INR between 2.0 and 3.0 [6,8]. Measurement of INR is routinely performed using a prothrombin time (PT) with either the Quick or Owrens method in diagnostic laboratories using a venous blood sample [9,10]. However, because frequent monitoring is required, many patients prefer to monitor their INR with point-of-care (POC) devices using capillary blood derived from a finger stick. It is known that LA interferes with phospholipid-dependent coagulation reactions [11], which can lead to prolonged PT and a falsely elevated INR value [1,12]. Whereas most INR reagents used in diagnostic laboratories are relatively insensitive to interference by LA, there are indications that reagents in POC devices are not [13, 14, 15, 16, 17]. Because INR values are used to adjust the dosage of VKA, accurate INR values are of utmost ML-098 importance. A falsely elevated INR will lead to a APH-1B lower dosage of VKA, increasing the risk of thrombotic events in these patients. The interference of LA with reagents in POC devices is thought to be dependent on the type of thromboplastins used. It is known that not only the recombinant thromboplastins that are used in these POC devices but also laboratory assays based on the Quick method, are more sensitive to antiphospholipid antibodies than conventional thromboplastins used with Owrens method [18]. Moreover, the dilution of ML-098 plasma used in Owrens method makes this assay less sensitive to antiphospholipid antibody interference [19,20]. Several studies described the use of POC devices for INR management in patients with APS [13,15, 16, 17,21,22]. Although most of these studies found POC devices more.