Detection Of Lupus Anticoagulant Research Articles

The lupus anticoagulant detection conundrum: A study of the prevalence of positive results and the performance of haemostasis tests

The lupus anticoagulant detection conundrum: A study of the prevalence of positive results and the performance of haemostasis tests

The lupus anticoagulant titer is associated with elevated antiphosphatidylserine/prothrombin immunoglobulin-M isotype antibody levels.

Clot based assays used for lupus anticoagulant (LAC) detection are typically interpreted in a qualitative fashion and may not reflect LAC potency. In this cross-sectional study, we describe a method for quantifying the LAC titer using serial (dependent) two-fold dilutions in normal pooled plasma. Serial dilutions of 51 residual plasma samples from 50 patients were tested using the Russell's viper venom screening time (DRVVT) and activated partial thromboplastin screening time (APTT) methodologies. The measured clotting times and the corresponding dilution factors were then used to derive a four-parameter logistic model. The LAC titer for each patient was interpolated as the sample dilution that corresponds to the upper reference interval limit of the corresponding assay. Calculated APTT and DRVVT LAC titers displayed a strong linear correlation (R2 = 0.84) between each other, but not with the degree of prolongation of the APTT/DRVVT screening time in the neat undiluted samples. Using data driven partitioning, patients could be grouped into low (<10) or high (≥10) DRVVT LAC titer. There were no significant differences in anticardiolipin (aCL) or anti-beta 2 glycoprotein 1 (aB2GPI) antibody levels or prevalence of thromboembolic events between low and high LAC titer groups. In contrast, antiphosphatidylserine/prothrombin (aPS/PT) IgM antibody levels, but not IgG, were significantly higher in the high LAC titer group. The degree of prolongation of the APTT/DRVVT screening time is not correlated with the LAC titer. Only aPS/PT IgM antibodies levels were strongly correlated with the LAC titers. Additional studies are warranted to determine clinical implications of high LAC titers.

Taipan snake venom time has high sensitivity for lupus anticoagulants in non-anticoagulated, triple positive antiphospholipid syndrome patients.

Dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) are the mainstay assays in lupus anticoagulant (LA) detection yet they have limitations, particularly in relation to interferences and specificity. The recently validated Taipan snake venom time (TSVT) screening with ecarin time (ET) confirmatory assays overcome many of those limitations due to the innate specificity engendered from direct prothrombin activation, and insensitivity to the effects of vitamin K antagonists (VKA). The present study aimed to further evidence diagnostic utility of TSVT/ET by performing them in samples from 116 nonanticoagulated patients with established triple-positive antiphospholipid syndrome (APS). Samples were identified in three expert centres who performed dRVVT, APTT and solid phase antiphospholipid antibody assays with reagents from a variety of manufacturers. All samples additionally received TSVT/ET analysis using standardised reagents. Ninety seven of 116 (83.6%) were dRVVT- and APTT-positive, 85/97 (87.6%) of which were TSVT/ET-positive, 9/116 (7.8%) were dRVVT-positive only, 6 of which were TSVT/ET-positive, and 10/116 (8.6%) were APTT-positive only, 5 of which were TSVT/ET-positive. 96/116 TSVT/ET-positivity returned a high sensitivity for LA of 82.8%. Low coefficients of determination revealed weak relationships between LA potency and anticardiolipin and anti-β2-glycoprotein I antibody titres for all three LA assays. TSVT/ET has high sensitivity for the clinically significant LA found in triple positive APS patients. TSVT/ET can establish multiple LA assay positivity in nonanticoagulated patients negative for one of dRVVT or APTT, and is the only assay pairing insensitive to VKAs, the recommended anticoagulation for APS.

Comparison of different algorithms for lupus anticoagulant detection: a single-center experience

BackgroundThe laboratory tests for lupus anticoagulant (LA) detection comprise complex and multistep coagulation testing procedures. There is no established gold standard assay or direct comparison of algorithms as recommended by different guidelines. ObjectivesThis study aimed to evaluate and compare the LA detection performance of different laboratory algorithms suggested by the existing guidelines. MethodsThe routine LA test data of 1801 plasma samples, including 188 LA-positive and 1613 LA-negative samples, were re-evaluated by applying the algorithms recommended by existing guidelines and were interpreted using various methods. Diagnostic performance indices for each LA detection algorithm were compared with those of the other algorithms. The efficacies of the different interpretation methods were analyzed to determine a suitable interpretation methodology for each assay. ResultsThe diagnostic performance for detecting LA varied by the algorithm and method of interpretation used. All laboratory algorithms displayed exceptional diagnostic performance with all diagnostic parameters of >90.0%. Nearly perfect agreement was observed in all algorithms when compared to the Clinical and Laboratory Standards Institute 2014 guideline interpreted by normalized screen-to-confirm ratio (NSCR) and mixing test–specific cutoff (MTC), as a reference assay (Cohen’s kappa coefficient, >0.90 [range, 0.94-1.00]). A combination of the index of circulating anticoagulant and NSCR was optimal for interpreting the activated partial thromboplastin time–based test, whereas a combination of the MTC and NSCR was suitable for the diluted Russell’s viper venom time–based test. ConclusionAll laboratory algorithms showed equivalent diagnostic performance. Establishing the best method of interpretation for each assay is recommended to improve LA detection performance.

Lupus Anticoagulant Detection under the Magnifying Glass.

Diagnosis of antiphospholipid syndrome (APS) requires the presence of a clinical criterion (thrombosis and/or pregnancy morbidity), combined with persistently circulating antiphospholipid antibodies (aPL). Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) that defines this rare but potentially devastating condition. For the search for aCL and aβ2-GP-I, traditionally measured with immunological solid-phase assays (ELISA), several different assays and detection techniques are currently available, thus making these tests relatively reliable and widespread. On the other hand, LA detection is based on functional coagulation procedures that are characterized by poor standardization, difficulties in interpreting the results, and interference by several drugs commonly used in the clinical settings in which LA search is appropriate. This article aims to review the current state of the art and the challenges that clinicians and laboratories incur in the detection of LA.

Analytical dilemmas in lupus anticoagulant detection

Accurate lupus anticoagulant (LA) detection is crucial to antiphospholipid syndrome (APS) diagnosis. Detection is based on LA functional behavior in coagulation assays irrespective of epitope specificity. LA screening tests employ dilute phospholipids to accentuate in vitro inhibition by LAs, although they are not LA-specific and can be elevated by other coagulation abnormalities. Elevated screening tests are reflexed to mixing tests to distinguish between factor deficiency and inhibition. Confirmatory tests with high phospholipid concentration swamp LA to generate shorter clotting times than screening tests, whilst prolongation persists with non-phospholipid-dependent inhibitors. LA heterogeneity means that no single screening test detects every LA and the screen/mix/confirm medley must be applied to at least two assay types, usually dilute Russell’s viper venom time (dRVVT) and an LA-sensitive activated partial thromboplastin time (aPTT). Most laboratories restrict LA testing to these two assays, yet others, such as dilute prothrombin time (dPT), can perform with equal diagnostic efficacy, and additionally detect LA unreactive with dRVVT and aPTT. Converting clotting times to normalized ratios improves assay performance, and practitioners must choose between normal pooled plasma (NPP) clotting time denominators to reflect on-the-day assay performance, or reference interval (RI) mean clotting times to negate the effects of NPP variation. Cut-offs can be generated parametrically from normally distributed data, or different percentiles applied depending on the preferred balance between sensitivity and specificity. Sourcing sufficient donors for accurate cut-off estimations is problematic and transference exercises can be undertaken on low donor numbers. Analytical limitations of mixing tests have led to the adoption of alternative algorithms to the screen/mix/confirm test order, whilst some continue to rigidly apply the latter despite those limitations. Strategies to reduce or eliminate the effects of therapeutic anticoagulation have limitations, whilst the Taipan snake venom time (TSVT) screening test with an ecarin time (ET) confirmatory test is insensitive to vitamin K antagonist (VKA) and direct activated factor X anticoagulation.

Considerations for simultaneous detection of autoantibodies to coagulation factor and lupus anticoagulant

In patients with autoimmune coagulation factor deficiency (AiCFD), the production of autoantibodies that inhibit coagulation factors in the blood reduces the activity of those relevant coagulation factors, resulting in severe bleeding symptoms. Recently, reports of patients with AiCFD have noted the concomitant detection of lupus anticoagulant (LA), a risk factor for thrombosis. LA-positive patients may show bleeding symptoms due to decreased activity of coagulation factor II (FII) caused by autoantibodies against FII, in addition to thrombotic symptoms, a condition termed LA-hypoprothrombinemia syndrome (LAHPS). Anti-FII antibodies in LAHPS cases are frequently cleared antibodies that can be detected using immunological techniques, such as enzyme-linked immunosorbent assay (ELISA). Recently, several cases of coagulation FV inhibitors, known as autoimmune FV deficiency, have been reported. Some of these cases may be complicated by LA, which can cause thrombosis. False-positive results for anticoagulant inhibitors are known to occur in LA cases; therefore, immunological confirmation of antibodies against coagulation factors is recommended. Additionally, acquired hemophilia A (AHA), caused by autoantibodies against FVIII, is a typical acquired hemorrhagic diathesis, although affected patients may present with thrombosis associated with LA. Thus, it is important to remember that hemorrhagic diathesis due to autoantibodies against clotting factors can also result in thrombosis, as demonstrated by the co-detection of LA. When clotting factor inhibitors are detected in LA-positive individuals, it is important to confirm the presence of autoantibodies against coagulation factors using immunological methods, such as ELISA, to avoid false-positive results.

Direct oral anticoagulant adsorption and laboratory detection of lupus anticoagulant.

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. 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. 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). 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.

Evaluating the Relationship Between Antiphospholipid Antibodies and COVID-19 Severity.

Coronavirus 2 (COVID-19) has emerged as a new global pandemic, causing severe acute respiratory syndrome. Furthermore, the existence of antiphospholipid (APL) antibodies (Abs) and ultimately patient death may be linked to the occurrence of thrombotic events in patients with COVID-19. We aimed to investigate if there was a link between the presence of APL Abs and the severity of COVID-19 disease in patients at the Vali-Asr Hospital in Zanjan from June to July 2021. Real-time PCR was used to diagnose COVID-19 in 76 hospitalized patients. A total of 38 patients were hospitalized in the internal medicine ward and another 38 people were admitted to the intensive care unit of the Vali-Asr Educational Hospital in Iran's Zanjan region. Lupus anticoagulant (LAC) detection was done using the dilute Russell viper venom time method, and tests for anticardiolipin (ACL) Abs, IgG and IgM, and anti-beta2 glycoprotein 1 Abs, IgG and IgM, were done on blood and plasma samples of linked patients using the enzyme-linked immunosorbent assay technique. SPSS 24 was used to analyze data. Our findings showed that the presence of LAC was associated with disease severity in COVID-19 patients (p = 0.001). However, there was no significant relationship between APL Abs and mortality in patients affected with COVID-19. The evaluation of APL Abs, particularly LAC, in COVID-19 patients appears to be helpful in predicting the severity of the disease.

Progress of lupus anticoagulant detection in venous thromboembolism

Lupus anticoagulant is one of the risk factors for venous thromboembolism, and the detection of lupus anticoagulant in patients with venous thromboembolism is important for the choice of treatment options and prognosis of treatment. There was no relevant literature to analyze and summarize the application progress of lupus anticoagulant detection in venous thromboembolism. In order to deepen the understanding of such patients, and help clinicians to conduct reasonable diagnosis, treatment and management of these patients, we reviewed the relevant epidemiology, test precautions, and the value of test results in venous thromboembolism and related treatments.

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

Objective: The aim of this study was to review the role of activated carbon (AC) in eliminating the interference of rivaroxaban in the detection of lupus anticoagulants (LAs). Methods: Normal pooled plasma was obtained as group N1, group N2 took 1 mL plasma from N1 and added AC, group N3 was prepared by mixing normal plasma with rivaroxaban, and group N3 was treated with AC according to our procedure, as group N4. Plasma from 22 patients was collected before and 6–12 h after rivaroxaban therapy, described as group P1 and group P2, respectively, and 1 mL plasma was taken from group P2 and treated with AC, as group P3. Anti-Xa and diluted Russell’s viper venom time (dRVVT)/silica clotting time (SCT) index in each group were measured and compared. Results: Rivaroxaban concentrations and anti-Xa had high intercorrelations in group N3, and the levels of anti-Xa and dRVVT/SCT index had high intercorrelations. After treatment with AC, influence of rivaroxaban was removed, with LA and coagulation factor assays not influenced. Rivaroxaban administration could affect LA assay results in patients, with all LA results increased. After treatment with AC, results of anti-Xa and LA tests recovered to the level before rivaroxaban therapy. Conclusions: We proposed a reference procedure for the LA detection of patients using rivaroxaban by AC, and activated carbon was proven to be a simple product to eliminate the interference of rivaroxaban.

Antiphospholipid antibodies in the obstetric antiphospholipid syndrome: Detection and antibodies profile at the Maternity and Neonatal Medicine Center of Monastir, Tunisia.

This study aimed to implement lupus anticoagulant (LAC) detection techniques according to the International Society on Thrombosis and Hemostasis (ISTH) recommendations, in the Biological Laboratory of the Maternity and Neonatal Medicine Center (Monastir, Tunisia) and to evaluate the profile and the prevalence of antiphospholipid antibodies (aPL) in the obstetric antiphospholipid syndrome (OAPS). We collected two groups: a "case group" (53 women who presented one or more obstetrical criteria of APS) and a "control group." LAC was detected following the four steps recommended by ISTH 2009. Anticardiolipin (aCL) and antibeta-2-glycoprotein I (aβ2GPI) antibodies testing were performed by enzyme-linked immunosorbent assay (ELISA). aPL were found in five patients: three patients with isolated LAC, one patient with isolated IgG aCL, and one patient with triple positivity (LAC, aCL IgM, aβ2GPI IgM). Concerning LAC, 13 (24.52%) of 53 patients had a screening step with at least one positive test. The mixing step was positive in four patients and then confirmed in the confirmatory test. Thus, the prevalence of LAC in our study group is 7.54%. Surprisingly, among these positive patients, one patient had an associated combined factor V (FV) and factor VIII (FVIII) deficiency. There is no single test and no algorithm that can detect all types of LAC. It seems that the recent 2020 ISTH algorithm allows a better detection of low activity LAC than the 2009 algorithm. In our study, the most frequently identified antiphospholipid antibodies were LAC more than aCL and aβ2GPI.

Cardiac manifestations in primary antiphospholipid syndrome and their association to antiphospholipid antibodies' types and titers-cross-sectional study of Serbian cohort.

Antiphospholipid syndrome (APS) is multisystem autoimmune coagulopathy with antiphospholipid antibodies (aPL) in its ground, manifested as a primary disease (PAPS) or in the setting of other conditions, most commonly systemic lupus erythematosus. The objective of this cross-sectional study was to investigate various cardiac manifestations and their possible relation to aPL type and titer in a Serbian cohort of PAPS patients. A total of 360 PAPS patients were analyzed and aPL analysis included detection of anticardiolipin antibodies (aCL: IgG/IgM), anti-ß2glycoprotein I (ß2GPI: IgG/IgM), and lupus anticoagulant (LA). Cardiac manifestations investigated were valvular lesions (comprehending valvular thickening and dysfunction not related to age and pseudoinfective endocarditis), coronary artery disease (CAD) with specific insight for myocardial infarction (MI), chronic cardiomyopathy (CMP), and acute decompensated heart failure (ADHF) as well as pulmonary hypertension (PH) and intracardiac thrombus presence. The prevalence of cardiac manifestations overall was 19.6%. There was a strong association between age and the majority of cardiac manifestations, as well as standard atherosclerotic risk factors. aCL IgG-positive patients had a higher prevalence of valvular lesions (p = 0.042). LA presence was significantly related to MI (p = 0.031) and PH (p = 0.044). CMP and ADHF were significantly related to higher titers of aCl IgG (p = 0.033, p = 0.025 respectively). Age and smoking were independent risk predictors for MI in PAPS with meaningful risk for LA positivity (OR 2.567 CI 0.671-9.820 p = 0.168). Certain cardiac manifestations in PAPS were related to certain aPL type and/or titer levels, imposing confirmation in prospective studies. Preventive actions, comprehending proper anticoagulant/antithrombotic therapy, and intense action against standard atherosclerotic risk factors are of utmost importance in this group of patients. Key Points • In Serbian patients with primary antiphospholipid syndrome (PAPS), prevalence of non-criteria cardiac manifestations was 19.6% and they were significantly related to certain antiphospholipid antibodies and titers. • Lupus anticoagulant was a meaningful predictor of myocardial infarction, enabling possible risk stratification and proper preventive and therapeutical strategies in this subgroup of PAPS patients. • Patients with high titers of aCL IgG are more prone to acute decompensated heart failure occurence, imposing careful follow-up of these patients • Based on the analysis of the Serbian PAPS cohort, even being non-criterial, cardiology manifestations are significantly present and inclusion of cardiologists in treatment and follow-up of these patients should be implied from the diagnosis establishment.

Snake Venoms in Diagnostic Hemostasis and Thrombosis.

Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of hemostatic disorders. The most widely used are those that affect coagulation, such as thrombin-like enzymes unaffected by heparin and direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid gold of coagulation activators is Russell's viper venom, since it contains activators of factor X and factor V. It is used in a range of clotting-based assays, such as assessment of factor X and factor V deficiencies, protein C and protein S deficiencies, activated protein C resistance, and probably the most important test for lupus anticoagulants, the dilute Russell's viper venom time. Activators of prothrombin, such as oscutarin C from Coastal Taipan venom and ecarin from saw-scaled viper venom, are employed in prothrombin activity assays and lupus anticoagulant detection, and ecarin has a valuable role in quantitative assays of direct thrombin inhibitors. Snake venoms affecting primary hemostasis include botrocetin from the jararaca, which can be used to assay von Willebrand factor activity, and convulxin from the cascavel, which can be used to detect deficiency of the platelet collagen receptor, glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of snake venoms available in diagnostic practice.

Diagnostic Challenges on the Laboratory Detection of Lupus Anticoagulant.

Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) which defines the rare but potentially devastating condition known as antiphospholipid syndrome (APS). Testing for LA is a challenging task for the clinical laboratory because specific tests for its detection are not available. However, proper LA detection is paramount for patients’ management, as its persistent positivity in the presence of (previous or current) thrombotic events, candidate for long term anticoagulation. Guidelines for LA detection have been established and updated over the last two decades. Implementation of these guidelines across laboratories and participation to external quality assessment schemes are required to help standardize the diagnostic procedures and help clinicians for appropriate management of APS. This article aims to review the current state of the art and the challenges that clinical laboratories incur in the detection of LA.

Detection frequency and duration of lupus anticoagulant circulation in COVID-19 patients

The aim of the work was to determine frequency of lupus anticoagulant (LA) detection in patients at various degrees of COVID-19 severity as well as duration of LA circulation after the infectious disease. The study included 103 patients with COVID-19. The patients were observed during the hospital care and in ambulance, if required. The patients were admitted to the departments of infectious diseases arranged at the V.I.Kulakov National Medical Research Center for Obstetrics, Gynecology, and F.I. Inozemtsev City Clinical Hospital. Treatment schedules and stratification of the patients by clinical severity was carried out in accordance with Interim Guidelines issued by the Ministry of Health of the Russian Federation for the prevention, diagnosis and treatment of new coronavirus infection (version 9). The following groups were formed: mild (n = 27), moderate (n = 55) and severe (n = 20). The patients were tested for LA positivity in the course of disease: on the day of starting medical care (with outpatient observation), or on the day of hospitalization; repeated tests were made before discharge (inpatients), and later, 1-2 months and 7 months after recovery. Lupus anticoagulant was determined by two independent tests (dRVVT and SCT), i.e., as a screening test and a confirmation test. At initial examination, LA was found in 50 patients (49%). The effect of LA in 98% of cases was observed with dRVVT test, as an increase of normalized ratio (NR). The maximum median value of NR was 1.54 (0.97: 2.1) was revealed in patients with severe course of COVID-19 (p 0.0001) compared with other groups and correlated with severity of the infectious process (r = 0.491, p 0.0001). In mild cases of COVID-19, LA was detected less often (4 cases, 14.8%) than in moderate severity cases (27, 49.1%), and severe patients (19, 95%) (p 0.05). Re-examinations of the patients before discharge from the hospital and 1-2 months later revealed high frequency of LA (p 0.05). However, no LA-positive test was found 7 months after discharge. In patients with COVID-19, high frequency of circulating LA was registered, depending on severity of the infectious process. In addition, we have first shown that persistence of the circulating LA over post-infectious period does not exceed 7 months.

Impact of a commercially available DOAC absorbent on two integrated procedures for lupus anticoagulant detection

BackgroundLupus anticoagulant (LA)-detection in anticoagulated patients is an unmet need, which becomes even more cogent with the introduction of direct oral anticoagulants (DOAC) that may lead to false-positive results. AimsWe aimed to investigate the effect of a commercially available DOAC absorbent on residual drug concentrations, and on integrated procedures for LA-detection. MethodsBlood from patients treated for atrial fibrillation with either dabigatran (n = 39), rivaroxaban (n = 55), apixaban (n = 47) or edoxaban (n = 47) were collected at peak and trough, and centralized for testing with two LA integrated procedures [i.e., the silica clotting time (SCT) and dilute Russel viper venom (dRVVT)] before and after DOAC absorbent exposure. ResultsThe commercially available DOAC absorbent investigated in this study proved effective in reducing the concentrations of all the investigated DOAC, although small residual drug was detected after absorption, especially in patients on edoxaban.Results mimicking LA were observed in patients on DOAC before absorbent exposure, especially for rivaroxaban when testing was performed with dRVVT (88% rate at peak and 20% at trough) and much less with SCT (12% at peak and 8% at trough). The correspondent rate of results mimicking LA in patients on rivaroxaban after exposure was reduced [dRVVT (peak 8%, trough 4%); SCT (peak and trough 8%)], but not abolished. ConclusionsOverall, in vitro DOAC absorbance by active charcoal compounds is a useful laboratory tool for LA-detection in patients on DOAC. Caution should however be exerted when used in daily practice.

Practical Considerations and Testing Nuances for the Detection of Lupus Anticoagulant: Do Low Phospholipid Screen Results, Assay Type, and Test Ratio Matter?

Lupus anticoagulant (LA) detection requires (1) prolongation of a phospholipid (PL)-dependent clot-based screening assay, (2) noncorrection upon adding normal pooled plasma, and (3) a confirmatory PL dependency test. Paired LA assays run screening and confirmatory tests simultaneously, with their test ratio (TR) or differences used to evaluate test results. We evaluated patients whose paired testing demonstrated PL dependence suggestive of LA, yet the low PL screen was not prolonged. Clinical and laboratory parameters are compared across (1) true positive (screen prolonged, TR positive) vs borderline (screen not prolonged, TR positive); (2) low-, moderate-, and high-TR subgroups; and (3) dilute Russell viper venom time (dRVVT) vs silica clotting time (SCT). Borderline samples are not statistically different from true positives in their rate of repeat LA positivity or association with other anti-PL antibodies. Compared with true positives, borderline dRVVT is more frequent in pregnancy, women, and younger age. Elevated activated partial thromboplastin time is more frequent in true-positive dRVVT and SCT vs borderline and with an increasing dRVVT TR. LA persistence is more frequent with an increasing SCT TR. In addition, dRVVT true positivity is more frequent with thromboembolic events, while SCT is more frequent with autoimmunity and pregnancy complications. Negative low-PL screens may not necessarily lack LA. A reevaluation of the laboratory criteria for LA detection may be needed.

VWF, Platelets and the Antiphospholipid Syndrome.

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of antiphospholipid antibodies (aPLs). Laboratory criteria for the classification of APS include the detection of lupus anticoagulant (LAC), anti-cardiolipin (aCL) antibodies and anti-β2glycoprotein I (aβ2GPI) antibodies. Clinical criteria for the classification of thrombotic APS include venous and arterial thrombosis, along with microvascular thrombosis. Several aPLs, including LAC, aβ2GPI and anti-phosphatidylserine/prothrombin antibodies (aPS/PT) have been associated with arterial thrombosis. The Von Willebrand Factor (VWF) plays an important role in arterial thrombosis by mediating platelet adhesion and aggregation. Studies have shown that aPLs antibodies present in APS patients are able to increase the risk of arterial thrombosis by upregulating the plasma levels of active VWF and by promoting platelet activation. Inflammatory reactions induced by APS may also provide a suitable condition for arterial thrombosis, mostly ischemic stroke and myocardial infarction. The presence of other cardiovascular risk factors can enhance the effect of aPLs and increase the risk for thrombosis even more. These factors should therefore be taken into account when investigating APS-related arterial thrombosis. Nevertheless, the exact mechanism by which aPLs can cause thrombosis remains to be elucidated.

Клинико-лабораторные изменения в системе гемостаза у пациентов с васкулитом зрительного нерва

Purpose. Clinical and laboratory studies of the hemostasis system in patients with optic nerve vasculitis. Materials and methods. Medical records and case history of 45 people (49 eyes) were analyzed, of which pathology in two eyes was detected in 4 people (8 eyes). The study involved 24 men and 21 women aged 17 to 35 years. The follow-up period ranged from 3 months to 5 years. Standard ophthalmic research methods and special research methods were used. Laboratory methods for the study of hemostasis included the detection of lupus anticoagulant was carried out using poison tests, as well as confirmatory tests with donor plasma and corrective phospholipids. Results. Retinopathy of the type of venous stasis was found in 30 people, neuropathy of the type of stagnant disc – in 15 people. In young patients after a viral infection with damage to the optic nerve in clinical form, retinopathy such as venous stasis and congestive optic nerve head with lupus anticoagulant was found in 73.4% of cases. In patients with vasculitis of the optic nerve with lupus anticoagulant, disturbances in the vascular-platelet and plasma-coagulation links in the hemostatic system were revealed. Conclusion. Lupus anticoagulant significantly reduces thromboresistance of the endothelium of the retinal microvasculature and enhances hypercoagulation, breaks the natural regulation of the hemostasis system and aggravates ischemia of the retina, optic nerve, participates in the pathogenesis of clinical forms of optic nerve vasculitis. Key words: hemostatic system, lupus anticoagulant, thrombophilia, optic nerve vasculitis.