Laboratory Diagnosis of Antiphospholipid Syndrome in Anticoagulated Patients

Antiphospholipid antibodies in patients with antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a rare systemic autoimmune disease characterized by recurrent pregnancy morbidity or thrombosis in combination with the persistent presence of antiphospholipid antibodies (aPLs) in plasma/serum. Antiphospholipid antibodies are a heterogeneous, overlapping group of autoantibodies, of which anti-β2-glycoprotein I (aβ2GPI), anticardiolipin (aCL) antibodies and antibodies that prolong plasma clotting time in tests in vitro known as lupus anticoagulant (LAC) are included in the laboratory criteria for the diagnosis of APS. The presence of LAC antibodies in plasma is indirectly determined by measuring the length of coagulation in two tests - activated partial thromboplastin time (aPTT) and diluted Russell's viper venom time (dRVVT). The concentration of aβ2GPI and aCL (immunglobulin G (IgG) and immunoglobulin M (IgM) isotypes) in serum is directly determined by solid-phase immunoassays, either by enzyme-linked immunosorbent assay (ELISA), fluoroimmunoassay (FIA), immunochemiluminescence (CLIA) or multiplex flow immunoassay (MFIA). For patient safety, it is extremely important to control all three phases of laboratory testing, i.e. preanalytical, analytical and postanalytical phase. Specialists in laboratory medicine must be aware of interferences in all three phases of laboratory testing, in order to minimize these interferences. The aim of this review was to show the current pathophysiological aspects of APS, the importance of determining aPLs-a in plasma/serum, with an emphasis on possible interferences that should be taken into account when interpreting laboratory findings.

How the Hemostasis Laboratory Can Help Clinicians to Manage Patients on Oral Anticoagulants

Oral anticoagulants are widely used to treat or prevent cardiovascular diseases in millions of patients worldwide. They are the drugs of choice for stroke prevention and systemic embolism in patients with non-valvular atrial fibrillation and prosthetic heart valves, as well as for treatment/prevention of venous thromboembolism. Oral anticoagulants include vitamin K antagonists (VKAs) and direct oral anticoagulants (DOACs). The hemostasis laboratory plays a crucial role in the management of treated patients, spanning from dose adjustment based on laboratory testing that applies to VKAs to the measurement of drug concentrations in special situations that apply to DOACs. This article aims to overview how the hemostasis laboratory can help clinicians manage patients on oral anticoagulants. Special interest is devoted to the international normalized ratio, used to manage patients on VKAs and to the measurement of DOAC concentrations, for which the role of the laboratory is still not very well defined, and most interferences of DOACs with some of the most common hemostatic parameters are not widely appreciated.

Celiac trunk thrombosis in a patient with antiphospholipid syndrome induced by median arcuate ligament compression: a case presentation and literature review

Median arcuate ligament syndrome (MALS) is a rare disorder caused by the compression of the celiac axis by the fibrous structure of the diaphragm called the median arcuate ligament. Patients with MALS are usually undiagnosed unless characteristic symptoms such as nausea and vomiting, postprandial pain, and weight loss are presented. We report a case of a 29-year-old patient diagnosed with MALS and secondary antiphospholipid syndrome (APS) that developed celiac trunk, common hepatic artery and splenic artery thrombosis. There is not enough information on MALS as a trigger of thrombosis in predisposed patients such as those with APS. However, the case gives rise to suspicion and highlights the diagnostic processes, especially for patients with APS presenting postprandial abdominal pain and weight loss. This review likewise aims at the importance of Doppler ultrasonography as a screening tool and computer tomography (CT) or magnetic resonance (MR) both in the angiography variant, especially to diagnose confirmation and underlying treatment options.

Determining Thrombogenicity: Using a Modified Thrombin Generation Assay to Detect the Level of Thrombotic Event Risk in Lupus Anticoagulant-Positive Patients

The aim of this study was to determine the thrombogenicity of lupus anticoagulant (LA) antibodies using a modified thrombin generation assay (TGA) with the addition of activated protein C (APC) in a group of 85 patients with LA-positive samples. Of these, 58 patients had clinical manifestations of antiphospholipid syndrome (APS) according to the Sydney criteria classification, i.e., each patient had thrombosis or foetal loss, and 27 patients did not show any clinical manifestations of APS. A comparison of the two groups' TGA results revealed statistically significant differences (Fisher's test p = 0.0016). The group of patients exhibiting clinical manifestations of APS showed higher thrombogenicity in 56.9% of patients, while the group of patients not yet exhibiting clinical manifestations of APS showed higher thrombogenicity in 25.9% of patients. There were no significant differences in the specificity of the TGA test between the groups of patients exhibiting similar clinical manifestations. Receiver operating characteristic curve analysis showed a more significant relationship (p = 0.0060) for TGA than for LA titre (p = 0.3387). These data suggest that the determination of LA thrombogenicity with the TGA assay leads to an increased prediction of the manifestation of a thromboembolic event. Our findings appear to be particularly relevant for the prediction of thrombotic events in patients with laboratory-expressed APS and no clinical manifestations.

Removing direct oral factor Xa inhibitor interferences from routine and specialised coagulation assays using a raw activated charcoal product

BACKGROUND

Direct oral anticoagulants (DOACs) are increasingly prescribed for the prevention and treatment of thrombosis. However, DOACs are associated with extensive interference in coagulation assays. Herein, we evaluate raw activated charcoal (AC) as an adsorbent material, to minimise DOAC-associated interferences in routine and specialised coagulation parameters on CS-series analysers (Sysmex, Kobe, Japan).

METHODS

Commercial human-derived non-anticoagulated plasma materials, with or without increasing concentrations of anticoagulant, were assayed for routine and specialised coagulation parameters before and after treatment with AC.

RESULTS

Treatment of non-anticoagulated plasma with raw AC had minimal impact on routine and specialised coagulation parameters available on the CS-series; however, clinically relevant prolongations of certain activated partial thromboplastin time (APTT)-based assays were observed after treatment. Furthermore, in apixaban- and rivaroxaban-containing plasma material, AC efficiently adsorbed therapeutic and supratherapeutic DOAC concentrations; and, treatment with raw AC resolved DOAC-associated interferences on all affected routine and specialised coagulation parameters.

CONCLUSIONS

Overall, raw AC efficiently adsorbed apixaban and rivaroxaban from human-derived plasma, without significantly affecting the majority of underlying routine and specialised coagulation parameters available on CS-series analysers.