Detection of lupus anticoagulant in the era of direct oral anticoagulants

Viewpoint: Lupus anticoagulant detection and interpretation in antiphospholipid syndrome

Lupus anticoagulant (LA) is a well-established risk factor for the clinical manifestations of antiphospholipid syndrome (APS). Accurate LA detection is an essential prerequisite for optimal diagnosis and management of patients with APS or aPL carriers. Variability remains a challenge in LA testing, with reliable detection influenced by multiple factors, including pre-analytical conditions, anticoagulation treatment, choice of tests and procedures performed, as well as interpretation of results, that can lead to false-positives or negatives. A standardised approach to LA testing, following current guidance, based on published data and international consensus, and with attention to detail, is required to underpin accurate detection of LA. Future work should focus on better characterisation of the nature of LA, which may ultimately lead to improved diagnosis and management of patients with APS and aPL carriers. This article reviews current practice and challenges, providing an overview on detection of LA.

Thrombin generation assay and lupus anticoagulant synergically distinguish populations of patients with antiphospholipid antibodies

AIM

To apply thrombin generation assay (TGA) in a large cohort of antiphospholipid antibodies (aPL)-positive patients.

MATERIAL AND METHODS

108 patients were tested with TGA and lupus anticoagulant (LA) testing and divided according to their aPL profile. Briefly, 21 patients were positive for anti-phosphatidylserine (aPS)/prothrombin (PT) IgG/IgM (group1), 29 for anti-ß2-glycoprotein-I (aβ2GPI) and anti-cardiolipin (aCL) IgG/IgM (group2), 31 for aPS/PT, aβ2GPI and aCL IgG/IgM (group3), 27 for aPS/PT and/or aβ2GPI+aCL IgM at low-titres (group4). 31 healthy donors (HDs) and 24 controls treated with vitamin K antagonists (VKA) were included.

RESULTS

The most deranged TGA and LA profiles were observed in tetra-positive patients (group3) that differed significantly to the other groups, thus those with isolated, double or triple aPL-positivity. Moreover, when comparing the TGA profile of all antiphospholipid syndrome (APS) patients, aPL-carriers, HDs and VKA controls, we observed that the aPL+ patients (especially APS) showed a distinctive profile that allowed to distinguish them from the other groups with significantly higher tLag and tPeak, and lower Peak and area under the curve.When focusing on APS clinical manifestations, patients with a high-risk profile (group3) showed significant differences from those presenting low-titres aPL (group 4) regarding the number of venous events (p=0.04), recurrence of any thrombotic event (p=0.01), of arterial events (5 vs 0, p=0.02), the occurrence of TIA (p=0.04), DVT (p=0.02) and, when analysing extracriteria manifestations, of peripheral artery disease (p=0.04).

CONCLUSIONS

TGA seems a valuable approach to stratify aPL+ patients according to their risk profile. The differences among different populations of autoantibodies specificities could be considered a translational validation of the increased thrombotic risk of patients with triple or tetra aPL-positivity.

16th International congress on antiphospholipid antibodies task force report on antiphospholipid syndrome laboratory diagnostics and trends

Classification criteria for antiphospholipid syndrome (APS) require IgG or IgM isotypes of the anticardiolipin (aCL) antibodies, anti-β2 glycoprotein I (anti-β2GPI) antibodies, and/or the lupus anticoagulant (LA) to satisfy the laboratory disease definition. Over the past 20 years, non-criteria antiphospholipid antibodies (aPL) directed to other proteins of the coagulation cascade (i.e. prothrombin and/or phosphatidylserine-prothrombin complex) or to some domains of β2GPI have been proposed. This task force concentrated and reviewed the literature on data including aPS/PT, antibodies to domain 4/5 of β2GPI and the newly described antibodies to protein/HLA-DR complex. In addition, we discussed testing of LA in the 'new' oral anticoagulants' era and the value of triple positivity in the risk assessment of aPL. The conclusions were presented at a special session during the 16th International Congress on aPL, Manchester, UK, September 2019.

Antiphospholipid Syndrome in Patients with Venous Thromboembolism

Unprovoked (or provoked by mild risk factors) venous thromboembolism (VTE) in young patients, VTE in uncommon sites, or cases of unexplained VTE recurrence may be positive for antiphospholipid antibodies (aPL) and thus may be diagnosed with antiphospholipid syndrome (APS). The evaluation of aPL is standardized using immunological tests for anticardiolipin and anti-β2-glycoprotein I. The determination of functional antibodies (lupus anticoagulant) is less standardized, especially in patients on anticoagulant treatment. Patients positive for all the three tests are at high risk of recurrence, which, in turn, might lead to chronic obstruction of pulmonary vessels (chronic thromboembolic pulmonary hypertension). Randomized clinical trials have shown that triple-positive patients should be treated with vitamin K antagonists maintaining an international normalized ratio between 2 and 3. Whether patients with VTE and incomplete aPL profile can be treated with direct oral anticoagulants should be further investigated.

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.

Antiphospholipid Syndrome and Kidney Involvement

BACKGROUND

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by the development of autoantibodies and the impairment of the coagulation system. Knowledge about this syndrome is increasing over time, but kidney involvement, especially APS nephropathy, still represents a challenge for physicians.

SUMMARY

A "two hit" model has been hypothesized to explain APS pathophysiology, and the role played by some factors, such as the complement system, is becoming more and more clear. From a clinical point of view, along with thrombosis in any site and/or obstetric morbidities, that are the hallmarks of APS, a constellation of several other clinical symptoms is related to APS. These symptoms alone are not sufficient to fulfill Sydney criteria for APS and this could potentially lead to omitting some diagnoses. The mainstay of management of APS is antithrombotic therapy, but there are expectations for new drugs that regulate the immune system. APS could affect the kidneys in many ways and among them, APS nephropathy is an intriguing entity that has been overlooked in recent years. Novel studies on APS nephropathy are lacking.

KEY MESSAGES

In this review, we discuss what we currently know about APS and its relationship with the kidney, with an eye toward the future perspectives. Multicenter studies on APS nephropathy are necessary in order to develop targeted therapies.

Laboratory Diagnosis of Antiphospholipid Syndrome in Anticoagulated Patients

The laboratory diagnosis of antiphospholipid syndrome (APS) requires the measurement of solid-phase antibodies to cardiolipin or β2-Glycoprotein-I and the search for lupus anticoagulant (LA). The diagnosis of patients whilst on anticoagulation is impaired by the difficult interpretation of results, at least for LA, owing to the fact that prolongations of clotting times induced by LA superimpose those induced by anticoagulants. This is a matter of concern as treating physicians very often need to know the APS status of their patients to make a decision on secondary antithrombotic prophylaxis. This article aims to review the effect brought about by anticoagulants on APS diagnosis and discuss the options that can be used to overcome such an effect.

Direct oral anticoagulant adsorption and laboratory detection of lupus anticoagulant

Direct oral anticoagulants (DOACs) interfere with many coagulation assays, mostly in lupus anticoagulant (LA) detection, causing false positive and negative results. Despite guidelines recommendations, LA testing may be important during anticoagulation when the clinician has to decide whether to prolong or discontinue the drug.

OBJECTIVES

In this study, the effect of activated charcoal (DOAC-Stop, DS) as a DOAC-adsorbent was investigated on samples from DOACs treated and untreated patients.

BASIC METHODS

165 plasma samples with a LA request were collected in three laboratories: 105 were from patients receiving DOACs and 60 were from nonanticoagulated patients with 30 LA negative and 30 LA positive. All coagulation screening assays and LA assays were evaluated before and after DS treatment.

RESULTS

The adsorption technique reduced DOACs concentration below the Lower Limit of Quantification. For nonanticoagulated patients: no significant difference in ratio results of coagulation screening (prothrombin time, activated partial thromboplastin time and thrombin time) and LA tests were observed before and after addition of DS in LA positive and negative patients. Every LA was correctly classified. For anticoagulated patients: a statistically significant difference was found for coagulation screening assays and LA assays. Final LA conclusions changed after DS addition from positive to negative in 58.9% of patients (more frequently with Rivaroxaban) and from negative to positive in 8% of patients (more frequently with Apixaban).

CONCLUSIONS

Our study suggests that DOAC-Stop can be used in daily laboratory practice to remove DOACs interference for a more accurate assessment of LA that is essential for diagnosis and management of APS patients.

"How we treat" clinical dilemmas in antiphospholipid syndrome: A case-based approach

Antiphospholipid syndrome (APS) is an autoimmune condition characterized by thrombosis (arterial, venous, and microvascular) and/or pregnancy morbidity occurring in subjects persistently positive for antiphospholipid antibodies (aPL). While the APS classification criteria are being currently updated to improve homogeneity in clinical research, patients who seek medical treatment often have a variety of laboratory and clinical characteristics that may not completely fulfill the classification criteria for overt APS. Those cases might represent a challenge in terms of treatment and overall management. We aim to present a collection of challenging scenarios of patients who tested positive for aPL and to discuss available literature to guide the therapeutic strategies.

Antibodies to the phosphatidylserine/prothrombin complex in the diagnosis of antiphospholipid syndrome

Aim. To determine the significance of antibodies to the phosphatidylserine/prothrombin complex (aPS/PT) in patients with systemic lupus erythematosus (SLE) antiphospholipid syndrome (APS). Materials and methods. A total of 190 patients were included in the study: 123 (64.7%) with reliable SLE and 55 (29%) with PAPS. The control group included 100 relatively healthy subjects of comparable age. All patients were tested for classical aPL as well as IgG/IgM-anti-PS/PT by enzyme immunoassay. Results. Based on the average values of IgG/IgM aPS/PT of the control group, the levels of positivity were allocated mean (M) + 3 or 5 standard deviations (SD): M+3SD and M+5SD. IgG aPS/PT levels above 73.6 U/ml (M+5SD) were more accurate diagnostic, for IgM aPS/PT above 18.0 U/ml. IgG-aPS/PT were detected in 84 (44%) of 190 patients. Levels above diagnostic levels were detected in 68 (65%) of 104 patients with APS (55 with PAPS and 59 with SLE+APS). Thrombosis was significantly more common in patients with IgG aPS/PT compared with patients negative for IgG aPS/PT. Arterial but not venous thrombosis was associated with IgG aPS/PT positivity. Conclusion. The frequency of detection of IgG aPS/PT in the examined patients was 44%, IgM aPS/PT 29% and their combination 19% of 190 patients. Half of the patients with probable APS had positive IgG aPS/PT and third IgM aPS/PT. Median IgG aPS/PT were significantly higher in patients with APS compared to patients without APS and the control group. Thrombosis was associated with IgG aPS/PT. Arterial thrombosis was significantly more frequently reported in patients with IgG aPS/PT. The sensitivity of IgG aPS/PT for reliable APS at levels greater than 73.6 units/ml was 59%, specificity 92%, for IgM aPS/PT 35% and 91%, respectively.

Antiphospholipid Antibodies and Lipids in Hematological Malignancies

One of the main groups of lipids is phospholipids, which are mainly involved in forming cell membranes. Neoplastic processes such as cell replication have increased lipid synthesis, making tumor cells dependent on this synthesis to maintain their requirements. Antiphospholipid antibodies attack phospholipids in the cell membranes. Three main types of antiphospholipid antibodies are recognized: anti-β2 glycoprotein I (anti-β2GP-I), anticardiolipin (aCL), and lupus anticoagulant (LA). These types of antibodies have been proven to be present in hematological neoplasms, particularly in LH and NHL. This review on antiphospholipid antibodies in hematological neoplasms describes their clinical relationship as future implications at the prognostic level for survival and even treatment.

Direct Oral Anticoagulant removal by a DOAC filter: Impact on lupus anticoagulant testing - Evaluation on spiked and patient samples

Background

DOAC Filter (DF) is a new device to overcome interference in lupus anticoagulant (LAC) testing by direct oral anticoagulants (DOACs).

Objectives

We evaluated DOAC removal from plasma and elimination of DOAC interference in LAC testing by DF, and impact of DF on LAC assays in a representative patient cohort, including a comparison with DOAC-Stop (DS).

Methods

Normal pooled plasma (NPP) was spiked with increasing concentrations of apixaban, rivaroxaban, edoxaban, and dabigatran. DOAC and LAC was measured on untreated, DF-treated, and DS-treated spiked samples. Coagulation parameters and thrombin generation were measured on patient samples (n = 20) before and after DF. Patients treated with DOAC, vitamin K antagonist, or heparin and nonanticoagulated patient samples (n = 139) were tested for LAC before and after DF.

Results

In spiked NPP, levels were below the lower limit of quantification (LLoQ) after DF/DS treatment for all DOAC concentrations. Following DF, levels were below LLoQ for 53 of 56 DOAC-containing patient samples. Twenty-eight of 33 LAC-positive DOAC-containing samples became negative after filtration, whereas 5 remained LAC-positive (1/5 from a patient with antiphospholipid syndrome [APS]). Four LAC-positive DOAC-containing samples (from patients without APS), became negative after filtration, whereas they remained LAC positive after DS. In the non-DOAC patient groups following DF, LAC changed from positive to negative in 8 (due to a procoagulant effect) and vice versa in 2 cases.

Conclusion

DF reduces DOAC interference in LAC testing. As incomplete DOAC removal may occur, DOAC measurements should be performed after filtration. A procoagulant effect after filtration may lead to erroneous LAC results in non-DOAC-containing samples. Therefore, using DF should be restricted to DOAC-containing samples.

Evaluation of Activated Carbon Treatment on Overcoming the Interference of Rivaroxaban on the Detection of Functional Lupus Anticoagulant

OBJECTIVE

To study the role of activated carbon in eliminating the interference of rivaroxaban in the detection of lupus anticoagulants (LA).

METHODS

Normal pooled plasma (NPP) was obtained as Group N1, and Group N2 took 1ml plasma from N1 and added activated carbon; Group N3 was prepared by mixing normal plasma with rivaroxaban, and Group N3 was treated with activated carbon according to our procedure, as Group N4. Plasma from 22 patients was collected before and 6-12 hours after rivaroxaban therapy, described as group P1 and group P2 respectively, and 1ml plasma was taken from Group P2 and treated with activated carbon, as Group P3. Anti-Xa and dRVVT / SCT index in each group were measured and compared.

RESULTS

Rivaroxaban concentrations and anti-Xa had high intercorrelations in Groups N3, and the levels of Anti-Xa and dRVVT / SCT index had high intercorrelations. After treatment with activated carbon, influence of rivaroxaban was removed, with lupus anticoagulant and coagulation factor assays not influenced. Rivaroxaban administration could affect lupus anticoagulant assay results in patients, with all LA results increased. After treatment with activated carbon, results of Anti-Xa and lupus anticoagulant tests recovered to the level before rivaroxaban therapy.

CONCLUSIONS

We proposed a reference procedure for the LA detection of patients using rivaroxaban by activated carbon, and activated carbon was proven to be a simple product to eliminate the interference of rivaroxaban.

Recent Advances in Anticoagulant Treatment of Immune Thrombosis: A Focus on Direct Oral Anticoagulants in Heparin-Induced Thrombocytopenia and Anti-Phospholipid Syndrome

For more than 10 years, direct oral anticoagulants (DOACs) have been increasingly prescribed for the prevention and treatment of thrombotic events. However, their use in immunothrombotic disorders, namely heparin-induced thrombocytopenia (HIT) and antiphospholipid syndrome (APS), is still under investigation. The prothrombotic state resulting from the autoimmune mechanism, multicellular activation, and platelet count decrease, constitutes similarities between HIT and APS. Moreover, they both share the complexity of the biological diagnosis. Current treatment of HIT firstly relies on parenteral non-heparin therapies, but DOACs have been included in American and French guidelines for a few years, providing the advantage of limiting the need for treatment monitoring. In APS, vitamin K antagonists are conversely the main treatment (+/− anti-platelet agents), and the use of DOACs is either subject to precautionary recommendations or is not recommended in severe APS. While some randomized controlled trials have been conducted regarding the use of DOACs in APS, only retrospective studies have examined HIT. In addition, vaccine-induced immune thrombotic thrombocytopenia (VITT) is now a part of immunothrombotic disorders, and guidelines have been created concerning an anticoagulant strategy in this case. This literature review aims to summarize available data on HIT, APS, and VITT treatments and define the use of DOACs in therapeutic strategies.

Investigation of the Molecular Mechanism of Coagulopathy in Severe and Critical Patients With COVID-19

Coagulopathy is a frequently reported finding in the pathology of coronavirus disease 2019 (COVID-19); however, the molecular mechanism, the involved coagulation factors, and the role of regulatory proteins in homeostasis are not fully investigated. We explored the dynamic changes of nine coagulation tests in patients and controls to propose a molecular mechanism for COVID-19-associated coagulopathy. Coagulation tests including prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen (FIB), lupus anticoagulant (LAC), proteins C and S, antithrombin III (ATIII), D-dimer, and fibrin degradation products (FDPs) were performed on plasma collected from 105 individuals (35 critical patients, 35 severe patients, and 35 healthy controls). There was a statically significant difference when the results of the critical (CRT) and/or severe (SVR) group for the following tests were compared to the control (CRL) group: PTCRT (15.014) and PTSVR (13.846) (PTCRL = 13.383, p < 0.001), PTTCRT (42.923) and PTTSVR (37.8) (PTTCRL = 36.494, p < 0.001), LACCRT (49.414) and LACSVR (47.046) (LACCRL = 40.763, p < 0.001), FIBCRT (537.66) and FIBSVR (480.29) (FIBCRL = 283.57, p < 0.001), ProCCRT (85.57%) and ProCSVR (99.34%) (ProCCRL = 94.31%, p = 0.04), ProSCRT (62.91%) and ProSSVR (65.06%) (ProSCRL = 75.03%, p < 0.001), D-dimer (p < 0.0001, χ2 = 34.812), and FDP (p < 0.002, χ2 = 15.205). No significant association was found in the ATIII results in groups (ATIIICRT = 95.71% and ATIIISVR = 99.63%; ATIIICRL = 98.74%, p = 0.321). D-dimer, FIB, PT, PTT, LAC, protein S, FDP, and protein C (ordered according to p-values) have significance in the prognosis of patients. Disruptions in homeostasis in protein C (and S), VIII/VIIIa and V/Va axes, probably play a role in COVID-19-associated coagulopathy.

A Meta-analysis and Systematic Review of Valvular Heart Disease in Systemic Lupus Erythematosus and Its Association With Antiphospholipid Antibodies

BACKGROUND

Valvular heart disease (VHD) is a known cardiac manifestation of systematic lupus erythematosus (SLE). This systematic review aims to pool data from studies to estimate the frequency of valvular lesions in SLE patients. It also aims to demonstrate the association between VHD in SLE and antiphospholipid antibodies positivity.

METHODS

We included 27 studies after identifying relevant abstracts from PubMed, Scopus, and Google Scholar from the time of inception of database to 2019. Inclusion criteria consisted of English-language case-control and cohort studies. Three reviewers independently performed study selection, data extraction, and quality assessment using the Newcastle-Ottawa Scale for assessing risk for bias.

RESULTS

For VHD in SLE patients, the most commonly involved valve was the mitral valve, with 19.7% lesions being mitral regurgitation. In terms of morphological lesions, valve thickening (11.06%) and vegetations (11.76%) were among the most prevalent. Other commonly encountered lesions were mitral valve prolapse and tricuspid regurgitation in 9.25% and 10.86% of patients, respectively. A meta-analysis of 21 studies with 2163 SLE patients, of which 23.3% had valvular lesions, showed a significant association of anticardiolipin antibodies positivity with VHD (relative risk, 1.55; confidence interval, 1.10-2.18).

CONCLUSIONS

Systemic lupus erythematosus is associated with VHD, and it should be considered a clinical manifestation of SLE in the absence of other valvular pathologies. There is a clear association between VHD in SLE and immunoglobulin G anticardiolipin antibodies positivity. This association suggests that this subgroup of SLE patients might benefit from a screening echocardiogram.

Anti-Phosphatidylserine/Prothrombin Antibodies at Two Points: Correlation With Lupus Anticoagulant and Thrombotic Risk

Antibodies to phospholipids (aPL) and associated proteins are a hallmark in the diagnosis of anti-phospholipid syndrome (APS). Those included in the classification criteria are the lupus anticoagulant (LA) and the IgG and IgM isotypes of anticardiolipin (aCL) and anti-beta-2 glycoprotein I (β2GPI) antibodies. Non-classification criteria markers such as autoantibodies that recognize the phosphatidylserine/prothrombin (aPS/PT) complex have been proposed as biomarkers for APS. Studies of aPS/PT antibodies have shown a strong correlation to clinical manifestations and LA. We aimed to study the value and the persistence of aPS/PT IgG and IgM antibodies in a cohort of consecutive patients with clinical suspicion of APS and their utility as thrombotic risk markers. Our study, with 103 patients, demonstrates that persistently positive results for aPS/PT IgG antibodies were significantly associated with APS classification, thrombosis, triple aPL positivity, LA positive result, and the Global APS Score (GAPSS) > than 9 points (p < 0.01, for each condition). On the other hand, no association was seen with pregnancy morbidity (p = 0.56) and SLE (p = 0.07). Persistence of aPS/PT antibodies, defined according to the current laboratory classification criteria, likely improves the diagnosis and clinical assessment of patients with APS.

Anti-phosphatidyl-serine/prothrombin antibodies (aPS/PT) in isolated lupus anticoagulant (LA): is their presence linked to dual test positivity?

OBJECTIVES

Anti phosphatidylserine/prothrombin antibodies (aPS/PT) are often present in patients with antiphospholipid syndrome (APS) and might be relevant in the pathogenesis of this condition. They are major determinant of lupus anticoagulant (LA) in triple-positive antiphospholipid (aPL) profile. Whether they are present and pathogenic in patients with isolated LA [negative anticardiolipin (aCL) and anti β2-Glycoprotein I (aβ2GPI) antibodies] is a matter of debate.

METHODS

We measured aPS/PT in a large number of isolated LA with the aim to ascertain whether there is a link between the way isolated LA is assessed and the presence of these antibodies. APS/PT were measured in 86 patients with isolated LA (aCL- and abeta2GPI-). LA was assessed by two test systems, the dilute Russell Viper Venom Time (dRVVT) and the Silica Clotting Time (SCT).

RESULTS

Sixty-six (77%) individuals with isolated LA were positive for aPS/PT (IgM 44, IgG and IgM 15, IgG in 7). Diagnosis of LA was made based on positive results in both dRVVT and SCT in 40 patients (Group 1) and based on only one positive test in the remaining 46 patients (Group 2). The rate of positive aPS/PT antibodies was significantly higher in Group 1 (OR=7.2, 95% CI 1.9-27.0, p<0.002). Moreover, the titre of IgM aPS/PT was significantly increased in Group 1 as compared to Group 2 (137 U, IQR 64-179 vs. 43 U, IQR 11-120, p=0.008).

CONCLUSIONS

These data indicate an association between LA based on two positive coagulation tests and the presence of aPS/PT antibodies, especially of IgM isotype.

Autoimmune Coagulation Factor X Deficiency as a Rare Acquired Hemorrhagic Disorder: A Literature Review

Coagulation factor X (F10) amplifies the clotting reaction in the middle of the coagulation cascade, and thus F10 deficiency leads to a bleeding tendency. Isolated acquired F10 deficiency is widely recognized in patients with immunoglobulin light-chain amyloidosis or plasma cell dyscrasias. However, its occurrence as an autoimmune disorder is extremely rare. The Japanese Collaborative Research Group has been conducting a nationwide survey on autoimmune coagulation factor deficiencies (AiCFDs) starting in the last decade; we recently identified three patients with autoimmune F10 deficiency (AiF10D). Furthermore, an extensive literature search was performed, confirming 26 AiF10D and 28 possible cases. Our study revealed that AiF10D patients were younger than patients with other AiCFDs; AiF10D patients included children and were predominantly male. AiF10D was confirmed as a severe type of bleeding diathesis, although its mortality rate was not high. As AiF10D patients showed only low F10 inhibitor titers, they were considered to have nonneutralizing anti-F10 autoantibodies rather than their neutralizing counterparts. Accordingly, immunological anti-F10 antibody detection is highly recommended. Hemostatic and immunosuppressive therapies may help arrest bleeding and eliminate anti-F10 antibodies, leading to a high recovery rate. However, further investigation is necessary to understand the basic characteristics and proper management of AiF10D owing to the limited number of patients.

In vitro diagnostics for the medical dermatologist. Part II: Hypercoagulability tests

The skin often provides initial clues of hypercoagulability with features such as livedo reticularis, livedo racemosa, retiform purpura, necrosis, and ulcerations. Because these cutaneous manifestations are nonspecific, laboratory testing is often needed to evaluate for underlying causes of hypercoagulability. Importantly, these disorders are reported to be the most common mimicker, resulting in an erroneous diagnosis of pyoderma gangrenosum. Understanding inherent properties of, and indications for, available tests is necessary for appropriate ordering and interpretation of results. Additionally, ordering of these tests in an indiscriminate manner may lead to inaccurate results, complicating the interpretation and approach to management. This second article in this continuing medical education series summarizes information on methodology, test characteristics, and limitations of several in vitro laboratory tests used for the work up of hypercoagulability and vasculopathic disease as it pertains to dermatologic disease.

DOAC-Stop in lupus anticoagulant testing: Direct oral anticoagulant interference removed in most samples

BACKGROUND

The use of direct oral anticoagulants (DOACs) is a convenient therapeutic option for patients at risk of thrombosis. DOACs interfere with clot-based testing for the identification of lupus anticoagulant antibodies (LACs) in patients with antiphospholipid syndrome (APS), a common cause of acquired thrombotic disease.

OBJECTIVES

To evaluate a commercially available reagent DOAC-Stop for the removal of DOAC interference encountered in LAC testing.

PATIENTS/METHODS

We collected a cohort of 73 test samples from patients on DOAC therapy identified at a large institutional coagulation laboratory from March to December 2019, along with samples from 40 LAC positive and negative control patients not on therapy. Samples were treated with DOAC-Stop and tested for anti-Xa activity and thrombin time for the removal of apixaban, rivaroxaban, argatroban, and dabigatran activity from patient samples. Treated and untreated samples were tested using the activated partial thromboplastin time, silica clotting time, and dilute Russell's viper venom time to evaluate the reliability and utility of DOAC-Stop.

RESULTS

DOAC-Stop markedly reduced DOAC interference from test samples (P < .05). DOAC-Stop had no effect on LAC testing in the absence of DOAC therapy, permitting the identification of all LAC positive and negative controls. DOAC-Stop removed false positives and false negatives resulting from DOAC interference and allows the identification of patients meeting criteria for the diagnosis of APS by LAC testing, as well as the detection of patients on rivaroxaban who are triple positive for APS.

CONCLUSIONS

DOAC-Stop is an effective adjunct for the clinical laboratory faced with DOAC interference in LAC testing.

Testing for antiphospholipid antibodies: Advances and best practices

The diagnosis of antiphospholipid syndrome (APS) relies on the detection of circulating antiphospholipid antibodies (aPL). Currently, lupus anticoagulant (LAC), anticardiolipin (aCL), and antibeta2-glycoprotein I antibodies (aβ2GPI) IgG or IgM are included as laboratory criteria if persistently present. Progress has been made on the standardization of tests as guidelines on LAC testing and immunological assays for aCL and aβ2GPI are published. However, LAC measurement remains a complicated procedure with many pitfalls and interfered by anticoagulant therapy. Solid-phase assays for aCL and aβ2GPI still show interassay differences. These methodological issues make the laboratory diagnosis of APS challenging. In the interpretation of aPL results, antibody profiles help in identifying patients at risk. Noncriteria aPL, such as antibodies against the domain I of beta2-glycoprotein (aDI) and antiphosphatidylserine-prothrombin (aPS/PT) antibodies have been studied in the last years and may be useful in risk stratification of APS patients. But, aDI and aPS/PT are not included in the current diagnostic criteria and testing in daily practice is not recommended as these antibodies have no added value in the diagnosis of APS. This review will focus on the technical aspects of the laboratory methods, the clinical relevance of assays and interpretation of aPL results in the diagnosis of APS.

The Effect of Direct Oral Anticoagulants on Antithrombin Activity Testing Is Abolished by DOAC-Stop in Venous Thromboembolism Patients

CONTEXT.—

Direct oral anticoagulants (DOACs) may cause false negative results of antithrombin (AT) deficiency screening.

OBJECTIVE.—

To evaluate the impact of DOAC-Stop, an agent reversing in vitro effects of DOACs, on AT testing in anticoagulated patients.

DESIGN.—

We assessed 130 venous thromboembolism patients aged 46.7 ± 13.5 years. Blood samples were collected 2 to 27 hours after DOAC intake from 49 patients on rivaroxaban, 54 on apixaban, and 27 on dabigatran. Antithrombin activity was assessed using the activated factor X (FXa)-based and the activated factor II (FIIa)-based method twice, before and after DOAC-Stop treatment, together with plasma DOAC levels using coagulometric assays.

RESULTS.—

The use of DOAC-Stop did not influence AT activity measured using the FIIa-based assay, whereas there was a marked decrease in AT activity determined using the FXa-based assay (ΔAT = 16.9%; 95% CI, 12.9%-19.1%). The AT-FIIa assay revealed decreased AT level (<79%) in all 10 (7.7%) genetically confirmed AT-deficient patients treated with rivaroxaban or apixaban (n = 5 each), whereas the AT-FXa assay showed decreased AT activity (<83%) in 2 subjects on rivaroxaban and 1 on apixaban with low plasma DOAC concentrations (<90 ng/mL). After DOAC-Stop median AT-FXa activity lowered from 83.5% (interquartile range, 66%-143%) to 65.5% (interquartile range, 57%-75%; P = .005; ΔAT = 18%) in AT-deficient patients, without any false negative results. The ΔAT in the FXa-based assay correlated with rivaroxaban and apixaban concentrations in the AT-deficient patients (r = 0.99, P < .001).

CONCLUSIONS.—

Application of DOAC-Stop enables reliable evaluation of AT deficiency screening in patients taking rivaroxaban or apixaban and tested using the FXa-based method.

Correlation Analysis of Anti-Cardiolipin Antibody/D Dimer/C-Reactive Protein and Coronary Artery Lesions/Multiple-Organ Damage in Children With Kawasaki Disease

Aim: Kawasaki disease (KD) is a systemic vasculitis with unknown etiology. In addition to cardiovascular system involvement, it can also have other multiple organs involved. This study is aimed at investigating the correlation between anti-cardiolipin antibody (ACA)/D dimer/C reactive protein (CRP) and coronary artery lesions (CAL)/multiple-organ lesions in children with KD. Methods: Retrospective analysis was performed in 284 KD/IKD patients from May 2015 to April 2016. Among them, 175 were males (61.6%), with average age of 2 years and 5 months old. Patients were divided into ACA+ group and ACA- group, elevated D dimer group (DDE) and normal D dimer group (DDN), and coronary artery injury (CAL) group and non-coronary artery injury (NCAL) group. Results: ACA was most likely tested positive in younger KD children (p < 0.05). ACA+ and hypoproteinemia were correlated with CAL, thrombocytosis, and granulocytopenia (p < 0.05-0.01). Levels of cTnI and CK in the CAL group were significantly higher than those in the NCAL group (p < 0.05). CAL was more frequently detected in younger patients and patients with prolonged fever, later IVIG treatment, and elevated CRP over 100 mg/l, but there was no statistically significant difference (all p > 0.05). In the KD with DDE group, the incidence of granulopenia, thrombocytosis, myocardial damage, cholestasis, hypoproteinemia, and aseptic urethritis was significantly higher than that in the KD with DDN group (p < 0.05-0.01). However, elevated D dimer was not associated with CAL. CRP elevation was highly correlated with D dimer, but not with CAL. Conclusion: Higher incidence of CAL and myocardial damage occurred in KD patients with positive ACA and hypoproteinemia. In the current study, ACA was only tested for positive and negative, which is a limitation to this study. To further elucidate the association, ACA titers would establish its significance in drawing a conclusion for the significance of ACA in CAL and myocardial damages. In addition, higher incidence of CAL occurred in younger patients. The higher D dimer was associated with increased multiple-organ damage (MOD). CRP was closely correlated with D dimer, but not correlated with ACA and CAL.

Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the International Society on Thrombosis and Haemostasis: Update of the guidelines for lupus anticoagulant detection and interpretation

This guidance focuses on methodological aspects of lupus anticoagulant (LA) testing, as well as interpretation of results for clinicians. The main changes in how to test for LA compared with the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee 2009 guidelines, in the preanalytical phase are more detailed recommendations on how to handle testing in anticoagulated patients, and the timing of testing. Also, routine coagulation tests are advised to obtain more information on the coagulation background of the patient, and when necessary, anti-Xa activity measurement for heparins or specific assays for direct oral anticoagulants should be performed. The three-step procedure with two test systems (diluted Russell's viper venom time and activated partial thromboplastin time [aPTT]) is essentially not changed. Silica remains the preferable activator in the aPTT assays, but ellagic acid is not excluded. We advise simultaneous performance of the mixing and confirmatory step, in each sample with a prolonged screening test. The confirmatory step can also be performed on a mixture of patient plasma and normal pooled plasma. Cutoff values should be established in-house on at least 120 normals, with transference of the manufacturer's cutoffs as an alternative. Reporting of results has not been changed, although more attention is focused on what clinicians should know. Patient selection for LA testing has been expanded.

Antiphospholipid syndrome in pediatric patients

PURPOSE OF REVIEW

The purpose of this review is to summarize the diagnosis and management of the antiphospholipid syndrome (APS) in children.

RECENT FINDINGS

APS is a rare, acquired autoimmune systemic disease that can result in significant morbidity in children related to vascular thrombosis. The diagnosis and management of APS in children can be challenging due to a lack of validated diagnostic criteria and the rarity of the disease. In addition, many healthy children have transient circulating antiphospholipid antibodies without thrombotic complications. Nevertheless, epidemiological studies suggest that APS represents a greater relative proportion of thrombotic disease in children than it does in adults. Management of pediatric APS is largely inferred from adult data despite unique characteristics of pediatric APS. The current recommendations include long-term anticoagulation, which can be problematic in young, active individuals. There is little data on potential benefits of nonantithrombotic therapy in the management of pediatric APS.

SUMMARY

Data on pediatric APS are limited, but evidence suggests that using current available diagnostic testing is valuable and, until further evidence is available, treating thrombotic complications with heparins or warfarin should be standard of care.

Unveiling the complex effects of direct oral anticoagulants on dilute Russell's viper venom time assays

INTRODUCTION

Dilute Russell viper venom time (dRVVT) assays can be affected by direct oral anticoagulants (DOACs), which may cause false-positive results. However, there are conflicting results indicating significant differences between different reagents and DOACs.

OBJECTIVES

To evaluate the effect of DOACs on dRVVT assays.

MATERIAL AND METHODS

Samples were prepared by adding DOAC (dabigatran, rivaroxaban, apixaban, or edoxaban) to pooled normal plasma in the concentration range 0 to 800 µg/L. Six integrated dRVVT reagents were used, all composed of a screen assay (low phospholipid content) and a confirm assay (high phospholipid content). The screen/confirm dRVVT results were expressed as normalized ratios. To further evaluate the observed differences between tests and DOACs, addition of synthetic phospholipids was used.

RESULTS

The dRVVT ratios increased dose dependently for all DOACs, with four of the six tests and the DOAC rivaroxaban having the greatest effect. With one test, the ratios were almost unaffected with increasing DOAC concentration, whereas another test revealed a negative dose dependency for all DOACs. Variable DOAC effects can be explained by different effects on dRVVT screen and confirm clotting time. Adding synthetic phospholipids to samples containing rivaroxaban resulted in greatly reduced screen clotting times and thereby lower calculated dRVVT ratios.

CONCLUSIONS

There is a great variability in the dRVVT test result with different DOACs. The dRVVT ratios are unaffected for some reagents and this can be explained by an equal dose-dependent effect on both screen and confirm assays. The phospholipid type and content of the different reagents may contribute to the observed differences.

Direct oral anticoagulant adsorption: Impact on lupus anticoagulant testing-Review of the literature and evaluation on spiked and patient samples

BACKGROUND

Direct oral anticoagulants (DOACs) interfere with lupus anticoagulant (LAC) testing. DOAC-Stop (D-S) represents a preanalytical strategy to cope with this issue.

OBJECTIVES

To assess D-S's ability to remove DOACs from plasma and overcome DOAC interference in LAC assays and to evaluate D-S's applicability in a representative patient cohort with routine LAC request.

METHODS

Apixaban (30-933 ng/mL), edoxaban (31-1060 ng/mL), rivaroxaban (35-1020 ng/mL), and dabigatran (20-360 ng/mL) were spiked to normal plasma. Aliquots were treated with D-S or untreated before DOAC and LAC testing. Patient samples containing DOAC (n = 43), vitamin K antagonists (n = 25), heparins (n = 21), or no anticoagulants (n = 63) were tested for LAC before and after D-S.

RESULTS

Spiking experiments revealed false-positive LAC from low concentrations of DOACs except for apixaban. Following D-S, DOAC levels were below lower limits of quantification, except for apixaban at the highest concentration, and no false-positive LAC was obtained. DOAC levels were below lower limits of quantification after D-S in 39/43 DOAC-containing patient samples. For 23/29 LAC-positive DOAC-containing samples, LAC tests became negative after D-S, whereas 3/6 samples remaining positive were from patients with (high probability for) antiphospholipid syndrome. In the non-DOAC-treated groups, LAC changed from positive to negative in 10 and vice versa in 2 cases.

CONCLUSIONS

D-S limits DOAC interference in LAC assays. DOAC concentration measurement should be performed in D-S treated samples because incomplete removal may occur. Applying D-S to vitamin K antagonist-containing, heparin-containing, or not-anticoagulated samples may lead to erroneous LAC results. Therefore, D-S should only be used in plasma from DOAC-treated patients.

Lupus anticoagulant detection in anticoagulated patients. Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the International Society on Thrombosis and Haemostasis

BACKGROUND

The laboratory detection of lupus anticoagulants (LA) in anticoagulated patients represents a challenge and there is no consensus on the types of assays/procedures to be adopted.

OBJECTIVES

This communication of the International Society on Thrombosis and Haemostasis (ISTH), Scientific and Standardization Committee (SSC) aims to give guidance on the procedures to be adopted.

METHODS

Members of the ISTH-SSC on Lupus Anticoagulant/Antiphospholipid Antibodies reviewed the literature to search for evidence on the most appropriate assays/procedures to be adopted.

RESULTS

Anticoagulants are able to interfere with the tests used for LA detection, giving rise to occasional false-positive or false-negative LA. Some commercial tests include in their composition heparin-neutralizers able to quench unfractionated or low molecular weight heparin up to 1.0 U/mL. LA tests are less affected by low molecular weight heparin, but caution is needed in the interpretation of results. Vitamin K antagonists (VKAs) may affect LA detection. Dilution of test plasma into pooled normal plasma is not a reliable solution as false-negative or false-positive LA may occur. Direct oral anticoagulants (DOACs) affect LA detection. Hence, it is not recommended to attempt LA detection in those patients. The use of DOAC adsorbents is a promising solution and should be further investigated on LA-positive and LA-negative patient populations. Taipan/Ecarin tests may be a solution for VKAs and anti-FXa DOACs, but independent evidence on their value and standardized kits is needed.

CONCLUSIONS

LA detection during anticoagulation remains a challenge, especially for VKAs. DOAC removal by in vitro addition to plasma of appropriate absorbents is promising.

How to Interpret Antiphospholipid Laboratory Tests

PURPOSE OF THE REVIEW

This review focuses on the laboratory tests necessary for the diagnosis of antiphospholipid syndrome (APS). For the interpretation of the results of the tests for antiphospholipid antibodies (aPL), understanding of all pitfalls and interferences is necessary.

RECENT FINDINGS

Progress has been made on the standardization of aPL tests and current guidelines for detection of lupus anticoagulant (LAC), anticardiolipin antibodies (aCL), and antibeta2-glycoprotein I antibodies (aβ2GPI) are useful tools. LAC measurement remains a complex procedure with many pitfalls and interference by anticoagulant therapy. Solid phase assays for aCL and aβ2GPI still show inter-assay differences. Measuring LAC, aCL, and aβ2GPI allows making antibody profiles that help in identifying patients at risk. Other aPL, such as antibodies against domain I of beta2-glycoprotein I (aDI) and antiphosphatidylserine-prothrombin (aPS/PT) antibodies, may be useful in risk stratification of APS patients, but are not included in the current diagnostic criteria as no added value in the diagnosis of APS has been illustrated so far. The laboratory diagnosis of APS remains challenging. LAC, aCL, aβ2GPI IgG, and IgM should be performed to increase diagnostic efficacy, with an integrated interpretation of all results and an interpretative comment. A close interaction between clinical pathologists and clinicians is mandatory.

Evaluation of the DOAC-Stop Procedure by LC-MS/MS Assays for Determining the Residual Activity of Dabigatran, Rivaroxaban, and Apixaban

The effect of direct oral anticoagulants (DOACs) on laboratory tests dependent on the production of their targets, factor IIa and factor Xa (FXa), is a well-known problem and can cause both false positive and negative results. Therefore, the correct interpretation of tests performed in patients receiving DOACs is necessary to avoid misclassification and subsequent clinical consequences. However, even with significant experience, there are situations where it is not possible to assess the influence of some methods. Particularly important is the situation in the diagnosis of lupus anticoagulants using the dilute Russell viper venom timetest, which is based on direct FXa activation. A very promising solution to this situation is offered by the DOAC laboratory balancing procedure DOAC-Stop. For evaluating the effectiveness of this procedure, 60 (20 apixaban, 20 dabigatran, and 20 rivaroxaban) patients treated with DOACs were enrolled. All patient samples were analyzed for the presence of individual DOAC types and subsequently subjected to the DOAC-Stop procedure.We evaluated its effectiveness by our own high-performance liquid chromatography-coupled tandem mass spectrometrymethod, which simultaneously sets all high-sensitivity DOACs. Unlike coagulation tests based on the determination of the residual effects of DOACs on target enzymes, which is complicated by extensive interindividual variation, this methodology is highly specific and sensitive.The DOAC-Stop procedure eliminated dabigatran from 99.5%, rivaroxaban from 97.9%, and apixaban from 97.1% of participants in our group. Residual amounts did not exceed 2.7 ng/mL for dabigatran, 10.9 ng/mL for rivaroxaban, or 13.03 ng/mL for apixaban, which are safe values that do not affect either screening or special coagulation tests.

Consultative Interpretation for Lupus Anticoagulant by Expert Pathologist Reduces False-Positive Rates in the Era of Direct Oral Anticoagulants

BACKGROUND

The diagnosis of antiphospholipid syndrome requires detection of antiphospholipid antibodies (aPL). A retrospective review of our testing practices revealed that societal recommendations for lupus anticoagulant (LA) testing as part of aPL testing are largely not followed by clinicians, and there was a high proportion of positive LA results. Increasing direct oral anticoagulant (DOAC) usage creates additional challenges in identifying LA. This prompted us to establish an order set with pathologist consultation ("LA panel") and testing algorithm to reduce false-positive LA and to ensure optimal LA identification and best practices for interpretation and follow-up.

METHODS

The laboratory database was reviewed to determine the number of LA tests ordered and rate of LA positivity before and after the LA panel was instituted. We assessed the impact of pathologist consultation to minimize false-positive findings and on following diagnostic guidelines.

RESULTS

LA panels were ordered for 1146 patients. LA was detected in 10% (111 of 1146) by dilute Russel viper venom time (dRVVT) normalized ratio [includes dRVVT screen (dRVVTs) positive/lupus-sensitive partial thromboplastin time (PTT-LA) positive and dRVVTs positive/PTT-LA negative] and 20% (228 of 1146) by Staclot-LA (includes dRVVTs negative/PTT-LA positive and dRVVTs positive/confirm negative). There was a reduction of false-positive LA by Staclot-LA; previously, 48% positive. We saw increased cancellation of LA testing for interfering anticoagulants [6.8% (16 of 236) vs 14.4% (55 of 383); P = 0.0061]. There was also increased adherence to follow-up LA testing [3% (8 of 236) vs 13.8% (53 of 383); P ≤ 0.001].

CONCLUSIONS

Creating a predetermined order set and testing algorithm with pathologist consultation improved LA testing interpretation and diagnostic follow-up testing.

The effect of unfractionated heparin, enoxaparin, and danaparoid on lupus anticoagulant testing: Can activated carbon eliminate false-positive results?

BACKGROUND

Heparins and heparinoids interfere with functional clotting assays used for lupus anticoagulant (LAC) detection. However, current guidelines for LAC testing do not provide clear guidance on this matter.

OBJECTIVES

We aimed to assess to effect of unfractionated heparin (UFH), enoxaparin, and danaparoid on LAC assays over broad anti-Xa activity ranges and to evaluate whether activated carbon (AC) is able to neutralize these effects.

METHODS

UFH (0.1-3.0 IU/mL), enoxaparin (0.2-2.9 IU/mL), and danaparoid (0.6-2.2 IU/mL) were spiked to normal pooled plasma. AC was added at multiple activity levels. Anti-Xa assays and LAC tests were performed on all samples using Stago analyzers and reagents.

RESULTS

Abnormal activated partial thromboplastin time (APTT) screening and mixing tests were obtained at the lowest levels for all compounds. Abnormal APTT confirmation tests were seen from 2.5 and 1.9 anti-Xa IU/mL for enoxaparin and danaparoid, respectively. Abnormal dilute Russell's viper venom test (dRVVT) screening tests were obtained from 1.6, 1.4, and 1.1 anti-Xa IU/mL for UFH, enoxaparin, and danaparoid, respectively. Mixing tests were abnormal from 2.5 and 1.3 anti-Xa IU/mL for enoxaparin and danaparoid, respectively. Abnormal dRVVT confirmation results were seen for danaparoid only from 1.9 anti-Xa IU/mL. AC was unable to neutralize anti-Xa activity in plasma and overcome the effect of the tested anticoagulants on LAC assays but may cause prolongation of APTT clotting times.

CONCLUSIONS

UFH, enoxaparin, and danaparoid clearly affected LA tests; however, false-positive LAC conclusions were obtained at supratherapeutic enoxaparin and danaparoid levels only. AC may prolong APTT screen clotting times, requiring 3-step testing to avoid potential misdiagnosis of LAC.

Lupus anticoagulant diagnosis in patients receiving direct oral FXa inhibitors at trough levels: A real-life study

INTRODUCTION

Direct oral factor Xa inhibitors (xabans) induce false positive results for lupus anticoagulant (LA) diagnosis. Consequently, it is suggested not to perform LA testing in xabans patients although it may be useful in selected patients. In this monocentric study, we evaluated xabans impact at trough levels (ie, just before the next intake) on LA diagnosis in treated patients using dilute Russell viper venom time (dRVVT) and two LA sensitive activated partial thromboplastin time (aPTT).

METHODS

Sixty patients receiving rivaroxaban (30) or apixaban (30) were included. Plasma concentrations were measured using specific anti-Xa assays. LA testing was performed using one dRVVT (LAC-Screening^® /Confirm^® ; Siemens) and two LA sensitive aPTT-based assays (Hemosil^® Silica Clotting Time (SCT) Screen/Confirm; Werfen and Dade^® Actin^® Factor Sensitivity FSL/FS (Actin F); Siemens).

RESULTS

Median [min-max] concentrations were 23 [<18-68] for rivaroxaban and 42 ng/mL [19-99] for apixaban. dRVVT was positive in 93% of rivaroxaban and 40% of apixaban samples. SCT was positive in 40 and 30% and Actin F in 17 and 20% of samples respectively. Xabans affected more significantly dRVVT than aPTT-based assays (P < .001) with less false positive results with apixaban than with rivaroxaban samples irrespective of the assay used.

CONCLUSION

lupus anticoagulant diagnosis in rivaroxaban and apixaban samples drawn at trough levels remains questionable whenever positive results are obtained. If LA testing in apixaban samples might be useful to rule-out LA using dRVVT and/or aPTT-based assays, the wide majority of rivaroxaban samples would give false positive results.

The effect of DOAC-Stop on lupus anticoagulant testing in plasma samples of venous thromboembolism patients receiving direct oral anticoagulants

Background

Direct oral anticoagulants (DOACs) cause false positive lupus anticoagulant (LA) results. We assessed the impact of DOAC-Stop, reversing in vitro effects of DOACs, on LA testing in anticoagulated patients.

Methods

We assessed 75 venous thromboembolism patients aged 44.5±14.6 years. Blood samples were collected 2–28 h since intake of DOACs, including 50 patients on rivaroxaban, 20 on dabigatran and five on apixaban. LA testing was performed at baseline and after DOAC-Stop treatment. Positive LA was defined as the normalized (patient/standard plasma clotting time) LA screening and screening (LA1)/confirmation (LA2) ratios exceeding 1.2.

Results

LA diluted Russell’s viper venom time (dRVVT) normalized screening test revealed abnormal results in 73 (97.3%) and activated partial thromboplastin time (APTT)-LA in 49 (65.3%) patients. In six (8%) patients, antiphospholipid syndrome (APS) was diagnosed. dRVVT LA1/LA2 was abnormal in 35 (50.7%) patients taking DOACs. The APTT ratio was normal in all studied subjects. DOAC-Stop completely removed dabigatran and reduced by 98% rivaroxaban and by 92.3% apixaban concentrations (all p<0.05). After DOAC-Stop screening dRVVT remained prolonged in 34 (49.3%) patients (p<0.001), while dRVVT LA1/LA2 was abnormal in six (8.7%) subjects, with no association with DOAC concentrations at baseline and after DOAC-Stop. The APTT-LA screening test remained prolonged in five (7.2%) patients, while the APTT LA1/LA2 ratio was normal in those subjects. DOAC-Stop did not influence LA testing in APS patients.

Conclusions

Application of DOAC-Stop effectively reduced plasma DOAC concentrations leading to appropriate dRVVT results in up to 97% of VTE patients.

Routine Coagulation Tests in Patients With Nonvalvular Atrial Fibrillation Under Dabigatran and Rivaroxaban Therapy: An Affordable and Reliable Strategy?

Dabigatran and rivaroxaban, direct oral anticoagulants (DOACs), affect coagulation tests, and knowledge of their effects is important for therapeutic monitoring. Our aim was to examine the association between DOAC levels and routine coagulation tests in patients with nonvalvular atrial fibrillation. Samples from patients receiving dabigatran (150 mg) and patients receiving rivaroxaban (20 mg) were collected 2 hours after drug intake. Direct oral anticoagulant concentrations were determined using direct Hemoclot thrombin inhibitor (HTI) assay (HTI test) and a direct Xa inhibitor (Anti Xa-Riva). The routine coagulation measured included activated partial thromboplastin time (aPTT) and prothrombin time (PT). The median plasmatic dabigatran was 128.3 ng/mL (95% confidence interval [CI]: 93.7-222.6 ng/mL). The HTI exhibited a good correlation with aPTT (R² = 0.74; P < .0001). The median plasmatic rivaroxaban was 223.9 ng/mL (95% CI: 212.3-238.9 ng/mL). Anti-Xa-Riva correlated with PT (R² = 0.69, P< .0001) and aPTT (R² = 0.36, P < .001), but prolonged PT results were obtained, even below the rivaroxaban therapeutic range (20%). The routine coagulation tests were able to identify out of therapeutic range concentrations for dabigatran and rivaroxaban. We suggest the use of these screening tests to better understand and monitor the subtherapeutic concentrations of these DOACs.

Perioperative Thromboelastometry for Adult Living Donor Liver Transplant Recipients with a Tendency to Hypercoagulability: A Prospective Observational Cohort Study

Background

Hypercoagulability can lead to serious thromboembolic events. The aim of this study was to assess the perioperative coagulation status in liver transplant recipients with a tendency to hypercoagulability.

Methods

In a prospective observational study (South African Cochrane Registry 201405000814129), 151 potential liver transplant recipients were screened for thrombophilic factors from October 2014 to June 2017, and 57 potential recipients fulfilled the inclusion criterion of presenting two or more of the following thrombophilic factors: low protein C, low protein S, low anti-thrombin, increased homocystein, increased antiphospholipid IgG/IgM antibodies, increased lupus anticoagulant, and positive Factor V Leiden mutation. Seven patients were excluded from the study because they fulfilled the exclusion criteria of cancelling the liver transplantation, oral anticoagulation, or intraoperative treatment with rFVIIa. Accordingly, 50 patients were included in the final analysis. Thromboelastometry (ROTEM) (EXTEM, INTEM and FIBTEM) and conventional coagulation tests (CCT) were performed preoperatively, during the anhepatic phase, post reperfusion, and on postoperative days (POD) 1, 3 and 7. ROTEM was used to guide blood product transfusion. Heparin was infused (60-180 U/kg/day) postoperatively for 3 days and then was replaced by low-molecular-weight heparin (20 mg/12 h).

Results

FIBTEM MCF significantly increased postoperatively above reference range on POD 7 despite normal fibrinogen plasma concentrations (p < 0.05). Both EXTEM and INTEM demonstrated significant changes with the phases of transplantation (p < 0.05), but with no intra- or postoperative hypercoagulability observed. INTEM CT (reference range, 100-240 s) normalized on POD 3 and 7 (196.1 ± 69.0 and 182.7 ± 63.8 s, respectively), despite prolonged aPTT (59.7 ± 18.7 and 46.4 ± 15.7 s, respectively; reference range, 20-40 s). Hepatic artery thrombosis (HAT) and portal vein thrombosis (PVT) were reported in 12.0% and 2.0%, respectively, mainly after critical care discharge and with high FIBTEM MCF values in 57% on POD 3 and 86% on POD 7. Receiver operating characteristics curve analyses of FIBTEM MCF were significant predictors for thromboembolic events with optimum cut-off, area under the curve and standard error on POD 3 (>23 mm, 0.779 and 0.097; p = 0.004) and POD 7 (>28 mm, 0.706 and 0.089; p = 0.020). Red blood cells (mean ± SD, 8.68 ± 5.81 units) were transfused in 76%, fresh frozen plasma (8.26 ± 4.14 units) in 62%, and cryoprecipitate (12.0 ± 3.68 units) in 28% of recipients. None of the recipients received intraoperative platelet transfusion or any postoperative transfusion. Main transplant indication was hepatitis C infection in 82%. 76% of recipients included in this highly selected patient population showed increased lupus anticoagulant, 2% increased antiphospholipid IgG/IgM antibodies, 20% increased homocysteine, 74% decreased anti-thrombin, 78% decreased protein C, 34% decreased protein S, and 24% a positive Factor V Leiden mutation. Overall 1-year survival was 62%.

Conclusion

A significant postoperative step-wise increase in FIBTEM MCF beyond the reference range was observed despite normal fibrinogen plasma concentrations, and FIBTEM MCF was a predictor for thromboembolic events in this study population, particularly after POD 3 and 7 on surgical wards when CCTs failed to detect this condition. However, the predictive value of FIBTEM MCF for postoperative HAT and PVT needs to be confirmed in a larger patient population. A ROTEM-guided anticoagulation regime needs to be developed and investigated in future studies.

Prevalence and Significance of Non-conventional Antiphospholipid Antibodies in Patients With Clinical APS Criteria

Background: The biological diagnostics of antiphospholipid syndrome (APS) takes into account the persistent positivity for anticardiolipin and/or anti-β2GP1 antibodies and/or presence of lupus anticoagulant (LA). However, some non-conventional antiphospholipid antibodies have emerged that could help in the diagnosis of APS.

Objectives: To study the potential usefulness of non-conventional antiphospholipid antibodies in clinical practice.

Methods: Eighty-seven patients, aged from 15 to 92 years were included and classified in following groups: 41 patients positive for the conventional antibodies with clinical criterion of APS (31 with primary APS and 10 secondary), 17 seronegative APS (SNAPS) patients (i.e., persistent negativity for the conventional antibodies with a strong clinical suspicion of APS), 11 asymptomatic antiphospholipid antibodies carriers (i.e., persistent positivity for the conventional antibodies without clinical evidence of APS), and 18 patients presenting with a first thrombotic or obstetrical event. IgG and IgM were detected to the following antigens: phosphatidylserine/prothrombin (PS/PT) by ELISA, and phosphatidic acid, phosphatidyl-ethanolamine, phosphatidyl-glycerol, phosphatidyl-inositol, phosphatidylserine, annexin V, prothrombin by immunodot. Anti-β2GP1 IgA, and anti-β2GP1 domain 1 IgG were detected by chemiluminescence.

Results: Positivity for the non-conventional antibodies was correlated with APS severity; patients with catastrophic APS (CAPS) being positive for 10.7 (Median, Range: 5–14) non-conventional antibodies. 9/17 seronegative patients were positive for at least one of non-conventional antibodies. A study of non-supervised hierarchical clustering of all markers revealed that anti-PS/PT antibodies showed high correlation with the presence of LA. All patients with APS triple positivity (highest risk profile) exhibited also persistent positivity for anti-PS/PT antibodies.

Conclusions: Our data obtained from a prospective cohort constituted mainly by patients with primary APS, suggest that non-conventional APS antibodies may be useful for patients classified as SNAPS. They demonstrate the potential value of aPS/PT antibodies as a strong marker of APS. We propose that anti-PS/PT antibodies could be a surrogate APS biological marker of LA to classify in high-risk profile patients treated by direct oral anticoagulants (DOACs), in whom LA detection cannot be achieved.

The clinical value of assays detecting antibodies against domain I of β2-glycoprotein I in the antiphospholipid syndrome

As the clinical symptoms of the antiphospholipid syndrome (APS) frequently occur irrespective of the syndrome, diagnosis predominantly depends on the laboratory assays measuring the level or function of antiphospholipid antibodies (aPLs). β2-glycoprotein I (β2GPI) is increasingly accepted as the most important target of aPLs. Anti-β2GPI antibodies constitute a heterogeneous population, but current in vivo and in vitro evidence show that especially the first domain (DI) of β2GPI contains an important pathogenic epitope. This epitope containing Glycine40-Arginine43 (G40-R43) has proven to be cryptic and only exposed when β2GPI is in its open conformation. A previous study demonstrated a highly variable exposure of the cryptic epitope in commercial anti-β2GPI assays, with implications on correct patient classification. Unexpectedly, recent unpublished data revealed impaired exposure of the pathogenic epitope in the commercially available anti-DI chemiluminescence immunoassay (CIA) assay detecting specific antibodies directed to DI. In this review we summarize the laboratory and clinical performance characteristics of the different anti-DI assays in published data and conclude with inconsistent results for both the correlation of anti-DI antibodies with clinical symptoms and the added value of anti-DI antibodies in the classification criteria of APS. Additionally, we hypothesize on possible explanations for the observed discrepancies. Finally, we highly advise manufacturers to use normal pooled plasma spiked with the monoclonal anti-DI antibodies to verify correct exposure of the cryptic epitope.

Antiphospholipid syndrome – an update

Abstract. Antiphospholipid syndrome (APS) is an autoantibody-mediated acquired thrombophilia. It is characterized by the presence of antiphospholipid antibodies (APL) that are directed against phospholipid-binding plasma proteins, such as beta-2-glycoprotein I (b2GPI). Its main manifestations are recurrent vascular thromboses (so-called “thrombotic APS”) and pregnancy complications (“obstetric APS”). According to the current consensus criteria, a persistently positive functional lupus anticoagulant (LA) assay and/or the presence of anti-b2GPI and/or anti-cardiolipin antibodies, together with clinical symptoms, is mandatory for the diagnosis of APS. Other clinical features, such as thrombocytopenia, Coombs-positive haemolytic anaemia, heart valve disease, renal microangiopathy and neurologic disorders are also common in APL-positive patients. APS can be associated with other autoimmune disorders, such as systemic lupus erythematosus. In rare cases, catastrophic APS (CAPS) occurs, with the development of excessive thrombosis at multiple sites, usually affecting small vessels and leading to multi-organ dysfunction and organ failure. Treatment usually comprises antithrombotic therapy using antiplatelet and anticoagulant agents. However, there is no consensus concerning the intensity or duration of therapy. Despite apparently adequate anticoagulation, the risk of recurrent thrombosis remains high. For patients with CAPS, a combined therapeutic approach that includes anticoagulation, glucocorticoids, plasma exchange and/or intravenous immunoglobulin seems to be the best treatment option.

Keywords: Antiphospholipid syndrome, lupus anticoagulants, anti-cardiolipin, anti-beta-2-glycoprotein I, vascular thrombosis, pregnancy complication