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.

Systemic lupus erythematosus with inflammatory bowel disease-ulcerative colitis: case report.

A 30-year-old female presented to the rheumatology outpatient clinic of the Internal Medicine Department, Ain Shams University Hospital, Cairo, Egypt, complaining of a large right leg ulcer consistent with pyoderma gangrenosum. There was history of recurrent attacks of bleeding per rectum of one-year duration. During hospitalization she noticed blurring of vision in the left eye with diffuse blackish discoloration of the feet and toes, consistent with small-vessel vasculitis. Colonoscopy with biopsy and histopathology confirmed the diagnosis of inflammatory bowel disease-ulcerative colitis (IBD-UC). Meanwhile, the patient fulfilled the SLICC classification criteria for systemic lupus erythematosus (SLE): recurrent oral ulcers, positive antinuclear antibody testing, proteinuria >0.5 gm/24-hour urine, positive test for lupus anticoagulant and consumed C3 complement component. Herein we report a rare case of coexistence of SLE and IBD-UC.

Measurement of lupus anticoagulants: an update on quality in laboratory testing.

Lupus anticoagulants (LAs) are antiphospholipid antibodies that interfere with in vitro phospholipid-dependent clotting tests, but are associated in vivo with significant clinical manifestations such as recurrent pregnancy loss and venous and arterial thrombosis. Although their detection is important for the diagnosis of thrombotic disorders such as the antiphospholipid syndrome, laboratory identification has historically been fraught with many issues. These have included variability in the sensitivity of assays and reagents; high false-negative and false-positive detection rates; a lack of consensus for the use of mixing tests; and, to some extent, lack of compliance with guidelines published by the Lupus Anticoagulant/Antiphospholipid Antibody Scientific Standardization Committee of the International Society on Thrombosis and Haemostasis (ISTH). Since the most recently updated guidelines in 2009, external quality assurance (EQA) programs have conducted surveys to provide a "snapshot" of laboratory practices related to the investigation of LA and to identify problems and monitor improvements in testing for LA. This article will review the impact of the most recently updated ISTH guidelines for LA testing and discuss the findings of recent EQA surveys.

Comparison of six dilute russell viper venom time lupus anticoagulant screen/confirm assay kits.

BACKGROUND: The normalized dilute Russell viper venom time (DRVVT) ratio provides a robust assay methodology for lupus anticoagulant (LA) detection. OBJECTIVES: We evaluated six normalized DRVVT LA screen and confirm systems for inter-method consistency. Reagents were purchased from Diagnostica Stago, Inc. (Parsippany, NJ); Precision BioLogic Inc. (Halifax, Nova Scotia, Canada); Siemens Healthcare Inc. (Deerfield, IL); TCoag (Parsippany, NJ); Instrumentation Laboratories (Bedford, MA); and Sekisui Diagnostics (Pfungstadt, Germany). METHODS: For all assays, we employed the STA-R Evolution automated coagulometer, adhering to manufacturers' instructions. LA-positive and LA-negative plasma controls were purchased from Diagnostica Stago and pooled normal plasma (PNP) was purchased from Precision BioLogic. We computed the mean of the reference interval (MRI) and action limits for all kits using LA-negative aliquots from locally sourced normal subjects (n = 42). We then assayed locally sourced LA-positive plasmas (n = 43) and using analysis of variance compared uncorrected screen/confirm ratios and screen/confirm ratios that were normalized using MRI and mean PNP results. RESULTS: The grand mean action limit, MRI + 3 SD, derived from the local normal plasmas, was 1.2, confirming the manufacturers' recommended limits; however, limits must be locally computed. The all-sample p value was less than 0.001, indicating heterogeneity among ratios. When Sekisui ratios were excluded, the p value was 0.14, thus indicating that this method introduced the major difference among methods. Mean screen/confirm ratios computed from LA-positive specimens were 1.91 to 2.04 for reagent systems other than Sekisui, which instead yielded a mean ratio of 1.198, indicating that this method was relatively insensitive to LA. A negative bias was recorded by two lots from the Sekisui system for LA-positive specimens. Screen/confirm ratios from combined LA-positive and LA-negative samples generated a combined range of 1.59 to 1.67 for all reagents except Sekisui, which instead yielded 1.09. The within-run percent coefficient of variation (CV%) was less than 5.0% using all samples. Between-run CV% using Diagnostica Stago LA-positive and LA-negative controls was less than 5.5%. CONCLUSIONS: DRVVT screen/confirm ratios discriminate between LA-positive and LA-negative samples and generally provide acceptable reproducibility. Ratio results may vary among reagent-instrument combinations. In this study, normalization added little to the clinical result interpretation.

Clinical manifestations and anti-phospholipid antibodies in 712 patients with systemic lupus erythematosus: evaluation of two diagnostic assays.

OBJECTIVES: To evaluate the agreement and performance of two tests for aPLs with regard to association with manifestations of the APS in patients with SLE. METHODS: We investigated 712 SLE patients and 280 population controls. Cardiolipin and ß(2) glycoprotein-I antibodies were measured with routine ELISA and a new automated method. Three positivity cut-offs (99%, 90% of controls and recommended cut-off by manufacturers) were used. Associations with previous thrombotic events, thrombocytopenia and, in a subgroup of patients, obstetric morbidity (n = 296) were evaluated. Results were compared with the LA test, performed in 380 patients. RESULTS: Inter-test agreement was moderate (demonstrated by κ-values 0.16-0.71). Performance of the two tests was similar: at the 99th percentile cut-off, sensitivity for any thrombotic event ranged from 3.7% to 24.8%, while specificity was 84.7-97.7%. Regardless of assay, IgG isotypes were associated with venous thrombosis and ischaemic cerebrovascular disease, whereas aPLs of IgM isotype were weakly associated with ischaemic heart disease. Associations were greatly affected by aPL level. LA performed better than the specific aPL tests. LA was associated with any thrombotic event, odds ratio 5.4 (95% CI 3.1, 9.4), while the specific aPL tests ranged from non-significant to an odds ratio of 1.9 (95% CI 1.03, 3.4) using criteria cut-off. LA was also convincingly associated with other APS manifestations. CONCLUSION: In relation to thrombotic manifestations, there was moderate agreement but no clear advantages when comparing a routine aPL ELISA with an automated method. APL isotype and titre as well as LA positivity are important for risk assessment in SLE patients.

Common and specific associations of anti-SSA/Ro60 and anti-Ro52/TRIM21 antibodies in systemic lupus erythematosus.

Little information exists about the association of anti-SSA/Ro60 and anti-Ro52/TRIM21 with systemic lupus erytematosus (SLE) features. In this work, we analysed the associations of both anti-Ro reactivities with clinical and immunological manifestations in 141 SLE patients. Photosensitivity and xerophtalmia/xerostomia were found to be positively associated with both anti-SSA/Ro60 (P = 0.024 and P = 0.019, resp.) and anti-Ro52/TRIM21 (P = 0.026 and P = 0.022, resp.). In contrast, a negative association was detected regarding anti-phospholipid antibodies, anti-SSA/Ro60 having a stronger effect (P = 0.014) than anti-Ro52/TRIM21. Anti-SSA/Ro60 showed a specific positive association with hypocomplementemia (P = 0.041), mainly with low C4 levels (P = 0.008), whereas anti-Ro52/TRIM21 was found to be positively associated with Raynaud's phenomenon (P = 0.026) and cytopenia (P = 0.048) and negatively associated with anti-dsDNA (P = 0.013). Lymphocytes are involved in the relationship between anti-Ro52/TRIM21 and cytopenia since positive patients showed lower cell levels than negative patients (P = 0.036). In conclusion, anti-SSA/Ro60 and anti-Ro52/TRIM21 showed both common and specific associations in SLE. These data thus increase evidence of the different associations of the two anti-Ro specificities even in a particular disease.

Risk assessment in patients with antiphospholipid antibodies.

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the association of antiphospholipid antibodies (aPL) with thrombosis and/or pregnancy loss: classification criteria were defined in the updated international consensus held in Sidney in 2005. Vascular and obstetric manifestations display partially different pathogenetic mechanisms. Thrombosis develop as a result of local procoagulative changes upon triggers influence (second-hit theory). Pregnancy morbidity is thought to be dependent on placental thrombosis and complement activation. The laboratory tests include Lupus Anticoagulant (LA), a functional assay, and anticardiolipin (aCL) and anti-ß2-glycoprotein I antibodies detected by solid phase enzyme-linked immunosorbent assay (ELISA). The LA testing is relatively standardized while there's still significant interlaboratory discrepancy in ELISA tests. Current APS criteria are under discussion: since for vascular and obstetric APS, different pathogenetic mechanisms have been shown, some criteria variation could also be contemplated. What is the weight of aPL antibodies in provoking thrombosis and which contribution could be expected from aPL per se is debated. As thrombosis is generally considered to be multi-factorial, each case needs a risk-stratified approach. Any primary prophylaxis, intensity and duration of secondary prophylaxis should take into account aPL profile, other cardiovascular risk factors and systemic autoimmune diseases associated. We look forward to the publication of recommendations of the leading experts in the field, developed during the recent 14th International Congress in Rio de Janeiro, Brazil.

Laboratory identification of lupus anticoagulants.

The main laboratory characteristic of lupus anticoagulants (LA) is their ability to prolong phospholipid-dependent clotting time in vitro. The laboratory demonstration of LA requires a systematic approach combined with an awareness of the many variables that can affect test results. The ideal testing procedures are those sensitive enough to detect weak LA and specific enough so as not to produce incorrect conclusions. International guidelines have been published to assist laboratories in applying correct testing processes. The most recently published guidelines from the International Society on Thrombosis and Haemostasis update the criteria for detecting the presence of LA that were presented in the 1995 guidelines. Some of the specific recommendations relate to the key areas of setting cut-off levels for screening, mixing, and confirmatory procedures. The more challenging aspects of testing for LA include maintaining sensitivity and specificity of the assays, especially in the presence of anticoagulant therapy.

To mix or not to mix in lupus anticoagulant testing? That is the question.

Mixing patient and normal plasma has been used for many years to assist with making decisions on which direction to proceed for further investigation of abnormally prolonged coagulation tests, namely, either individual coagulation factor measurement or the search for circulating anticoagulants. Mixing tests, however, gained wide acceptance only after the so-called lupus-like anticoagulant (LA) phenomenon was described and were, therefore, included in the guidelines for LA detection issued by the working group of the International Society on Thrombosis and Haemostasis. Important though they may be considered, the dispute between those who advocate the use of mixing tests and those who deny their superiority (or their need) for LA detection is difficult to resolve. This article aims to provide a balanced view on this dispute. Based on the limited information provided by the literature one may conclude that the disadvantages of performing mixing studies are the fact that (1) they are time-consuming; (2) they require a suitable source of normal pool plasma; and (3) weak LA may be lost at diagnosis due to the dilution of index plasma into normal pooled plasma. On the contrary, performing mixing tests makes the occurrence of false-negative LA in patients who present with the so-called "lupus cofactor phenomenon" relatively unlikely and, therefore, justifies their performance even though the frequency of the occurrence of this phenomenon in LA-positive patients is still unknown.

Testing for lupus anticoagulants--fresh or frozen?

BACKGROUND: There are no previous studies reporting the effect of using frozen-thawed plasma on lupus anticoagulant ratios in kits with the combined screen and confirm assay. METHODS: In the following study we chose patients with elevated dilute Russel's viper venom test (dRVVT) normalized ratios and compared the test results of fresh to frozen-thawed plasma. Platelet counts ranged from 2 to 7×10(3)/µL (10(9)/L) after a second centrifugation before freezing. RESULTS: There were 13 out of 14 dRVVT test normalized ratios that decreased after freezing (p<0.001), leading to the misclassification of six of 14 patients with high values that decreased into the reference interval. CONCLUSION: The major finding of this study is that testing frozen-thawed plasma with platelet counts <10,000/µL (10(9)/L) results in a significant decrease in dRVVT ratios. Although there was a consistent decrease in SCT normalized ratios as well, it did not lead to misclassifications.

Antiphospholipid syndrome: laboratory detection, mechanisms of action and treatment.

The antiphospholipid syndrome (APS) identifies a condition at increased risk of vascular occlusion and/or pregnancy complications. Patients are defined as having APS if they have at least one clinical (vascular occlusion and/or pregnancy complications) and one laboratory criterion at the same time. The laboratory criteria that define APS are repeated positivity (confirmed 12 weeks apart) for lupus anticoagulants and/or antibodies targeted against cardiolipin or ß(2) -glycoprotein I immobilized on solid surfaces. Over the years, APS has attracted the interest of many medical specialties. The aim of this review is to provide an update on (i) the laboratory criteria that determine the presence of APS, (ii) how the antibodies increase the risk of vascular occlusion and foetal loss and (iii) the treatment of the related clinical events.

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

OBJECTIVES: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: Negative low-PL screens may not necessarily lack LA. A reevaluation of the laboratory criteria for LA detection may be needed.

[Laboratory evaluation of lupus anticoagulant in Israel].

Lupus anticoagulants (LAC) are antibodies which are detected by a prolongation of phospholipid-dependent coagulation assays, and are associated with thrombotic events and pregnancy complications in patients with the antiphospholipid syndrome. The antiphospholipid syndrome is defined by arterial or venous thrombosis and/or pregnancy morbidity and by laboratory diagnosis of antiphospholipid antibodies. The laboratory diagnosis is based on LAC and/or anticardiolipin and/or anti-beta2-glycoprotein I antibodies present in plasma, on two or more occasions at least 12 weeks apart. ALthough the presence of LAC correlates best with thrombosis, the Laboratory testing of LAC is not well standardized. In this article, the Laboratory evaluation of LAC will be explained, including the different tests that are recommended by the Israeli Sub-committee of Thrombosis and Hemostasis Laboratories, the possibility to evaluate LAC in patients treated with antithrombotic therapy, and how to report and interpret the results.

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.

[Seronegative antiphospholipid syndrome: Myth or reality?] / Syndrome des antiphospholipides « séronégatif ¼ : mythe ou réalité ?

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-ß2 glycoprotein I antibodies (aß2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.

Antiphospholipid Syndrome Committee of the Brazilian Society of Rheumatology position statement on the use of direct oral anticoagulants (DOACs) in antiphospholipid syndrome (APS).

BACKGROUND: The term Direct Oral Anticoagulants (DOACs) refers to a group of drugs that inhibit factor Xa or thrombin. Even though their use for treating different thrombotic or prothrombotic conditions is increasing recently, there is no compelling evidence indicating that those medications are safe in all antiphospholipid syndrome (APS) patients. METHODOLOGY: To address this issue, specialists from the Antiphospholipid Syndrome Committee of the Brazilian Society of Rheumatology performed a comprehensive review of the literature regarding DOACs use in APS to answer the three following questions: (1) potential mechanisms of action of these drugs that could be relevant to APS pathogenesis, (2) DOACs interference on lupus anticoagulant testing, and (3) the efficacy of DOACs in APS. POSITION STATEMENT: After critically reviewing the relevant evidence, the authors formulated 8 Position Statements about DOACs use in APS. CONCLUSION: DOACs should not be routinely used in APS patients, especially in those with a high-risk profile (triple positivity to aPL, arterial thrombosis, and recurrent thrombotic events). In addition, DOACs interferes with LA testing, leading to false-positive results in patients investigating APS.

Investigations from external quality assurance programs reveal a high degree of variation in the laboratory identification of coagulation factor inhibitors.

The laboratory has a key role in the initial detection of factor inhibitors and an ongoing role in the measurement of inhibitor titers during the course of inhibitor eradication therapy. The most commonly seen factor inhibitors are those directed against factor VIII (FVIII), usually detected either with the original or the Nijmegen-modified Bethesda assay. In addition, several circumstances can arise in which the laboratory may test samples that potentially reflect false identification of factor inhibitors. These include lupus anticoagulants and other events generally related to preanalytical variables, including incorrect sample presentations. This article reviews each of these elements, largely from the perspective of cross-laboratory studies undertaken within the framework of external quality assurance (EQA), a peer-laboratory process that aims to assess the ongoing performance of groups of similar laboratories. This review details the experience of the Royal College of Pathologists of Australasia Haematology Quality Assurance Program, and it also reflects on the experience of other EQA organizations. Our analysis reveals a wide variety of test practice among inhibitor testing laboratories, a wide variation in detected inhibitor levels in cross-tested samples, and substantial evidence of false-positive and false-negative detection of factor inhibitors. These findings hold some significance for the clinical management of patients affected by these inhibitors. There is still much need for standardization and improvement in factor inhibitor detection, and we hope that this report provides a basis for future improvements in this area.

Placental histomorphology in unexplained foetal loss with thrombophilia.

BACKGROUND & OBJECTIVES: Acquired and genetic thrombotic conditions, both organ and non organ specific, are associated with increased foetal wastage. This study was carried out to examine the placenta from women with abnormal pregnancies and a history of unexplained foetal loss, and to associate with maternal thrombophilia status. METHODS: Placentas from eight women with history of unexplained foetal loss were analyzed for histopathological characteristics. All the women were simultaneously screened for the common acquired and genetic thrombophilia markers i.e., lupus anticoagulants ( LA), IgG / IgM antibodies for anticardiolipin (ACA), beta2 glycoprotein 1 (beta2GPI) and annexin V, protein C (PC), protein S (PS), antithrombin III (AT III), factor V Leiden ( FVL) mutation, prothrombin (PT) gene G20210A, methylene tetrahydrofolate reductase (MTHFR) C 677T, endothelial protein C receptor (EPCR) 23 bp insertion and plasminogen activator inhibitor ( PAI-1 4G/5G) polymorphisms RESULTS: Six of eight women were positive for one or more thrombophilia markers. The placenta in all the cases except one, showed the characteristic features of infarct fibrin deposition and calcification. Among two women who were negative for thrombophilia, one showed clear evidence of thrombus in the placental sections while the other did not show any characteristic infarcts in the placental sections. INTERPRETATION & CONCLUSION: Our findings showed that the histopathological examination of the placentas confirmed thrombophilia as the aetiological cause of thrombosis in 6 of the 8 women. The presence of thrombus in a negative thrombophilia woman suggests yet unidentified thrombophilia markers or probably non-haemostatic factors causing thrombosis.

Dilute Russell viper venom time interpretation and clinical correlation: A two-year retrospective institutional review.

INTRODUCTION: The dilute Russell viper venom time (dRVVT) detects lupus anticoagulant (LA). International Society for Thrombosis and Haemostasis (ISTH) guidelines specify positivity criteria, which differ from the assay manufacturer's criteria. METHODS: Two years of dRVVT testing at our institution were reviewed. For patients with prolonged dRVVT screening times, we evaluated dRVVT results by ISTH and manufacturer's criteria and correlated with the results of other antiphospholipid syndrome (APS) testing (LA-sensitive activated partial thromboplastin time and antiphospholipid antibodies) and with history of thromboembolism and other APS manifestations. RESULTS: Approximately one-fifth of dRVVTs exhibited a prolonged screening time. Among first prolonged dRVVTs, 35% were positive by both ISTH and manufacturer criteria, 44% met neither criteria, and 20% were equivocal (positive by only ISTH or manufacturer). Positivity by ISTH guidelines alone correlated better with other positive APS tests than manufacturer criteria positivity. Positive dRVVTs by both criteria correlated even more strongly with other positive APS assays. We investigated the likelihood of eventual APS diagnosis depending on the testing indication. No patient tested for LA solely for prolonged screening aPTT was subsequently diagnosed with APS. In patients with thrombosis, prolonged dRVVT clotting time not meeting both ISTH and manufacturer criteria was rarely associated with eventual APS diagnosis. CONCLUSION: We examined the correlation of dRVVT results with other APS testing and clinical outcomes. Interpretation method impacted how dRVVT results related to other APS testing, and, in limited data, to clinical findings. Patients with prolonged dRVVTs meeting only one set of positivity criteria rarely received an APS diagnosis.

Laboratory testing for lupus anticoagulant (LA) in patients taking direct oral anticoagulants (DOACs): potential for false positives and false negatives.

We and others have previously highlighted the potential problems with testing of lupus anticoagulants (LA) in patients on anticoagulant therapy, including most recently as related to the direct oral anticoagulants (DOACs). Thus, current DOACs in use (e.g., dabigatran, a direct thrombin inhibitor, and apixaban and rivaroxaban, both direct Xa inhibitors), affect a wide variety of coagulation assays, including those used in LA investigation. The Russell viper venom time (RVVT) assay in particular, key to the investigation of LA, is highly sensitive to DOACs. LA is a marker of thrombophilia, and patients who have had a thrombosis may be placed on a DOAC. Thus, there is a high likelihood that LA testing will be requested on patients whilst they are on DOACs. In the current report, we have assessed data from our facility for the past two and a half years for all LA tests performed by RVVT testing, and have evaluated this data with respect to patient anticoagulant status. In total, there were 7170 test requests for RVVT associated testing during the period of data capture. Most LA-RVVT screen results (5008; ∼70%) were within normal limits, thereby excluding LA by RVVT method in most of the patient cohort. All DOACs led to a prolongation in both RVVT screen and confirm assays. However, rivaroxaban affected the screen more than the confirm, leading to higher RVVT ratios, whereas apixaban affected the confirm more than the screen, leading to lower RVVT ratios. LA testing in the presence of DOACs also led to lower intra-patient consistency in LA test results. We conclude that ex-vivo data appears to confirm the potential for false positive (with rivaroxaban) and potential for false negative (with apixaban) identification of LA in patients on DOAC treatment. We also make some recommendations in regards to such testing.