What is the significance of a dilute Russell viper venom time (dRVVT) of 42 seconds?

From the Guidelines

A dilute Russell viper venom time (dRVVT) of 42 seconds is elevated and suggests the possible presence of lupus anticoagulant (LA), requiring confirmation with additional testing, including mixing studies and confirmatory tests, before making a definitive diagnosis. This finding is based on the most recent guidelines for lupus anticoagulant detection, which recommend the use of dRVVT as a first-choice clotting test for detecting LA 1. The dRVVT test works by activating factor X directly through Russell viper venom, bypassing the intrinsic pathway and making it sensitive to lupus anticoagulant interference with phospholipid-dependent coagulation reactions.

Key Considerations

• The patient should be evaluated for antiphospholipid syndrome, especially if they have a history of thrombosis, recurrent pregnancy loss, or autoimmune disorders like systemic lupus erythematosus.
• Management typically involves anticoagulation therapy such as warfarin, heparin, or direct oral anticoagulants, depending on the clinical context and history of thrombotic events.
• The International Society on Thrombosis and Haemostasis (ISTH) recommends concurrent testing for LA, aCL IgG and IgM, and aβ2GPI IgG and IgM, as well as measurement of LA in citrated plasma according to the ISTH-SSC recommendations by a 3-step methodology (screening, mixing, and confirmation) with parallel testing in APTT and dRVVT as first-choice clotting tests 1.

Diagnostic Approach

• The diagnostic approach should include a 3-step methodology: screening, mixing, and confirmation, with parallel testing in APTT and dRVVT as first-choice clotting tests.
• The results should be expressed as a ratio of patient-to-PNP for all procedures (screening, mixing, and confirm), and a report with an explanation of the results should be given 1.
• The ISTH guidelines also recommend that two consecutive aPL tests be positive at least 12 weeks apart to rule out transient aPL positivity, which is not sufficient for APS diagnosis 1.

Clinical Implications

• The presence of lupus anticoagulant is a risk factor for thrombosis, and patients with a history of thrombosis or recurrent pregnancy loss should be evaluated for antiphospholipid syndrome.
• The management of patients with lupus anticoagulant should involve a multidisciplinary approach, including hematologists, rheumatologists, and obstetricians, to ensure optimal care and prevent thrombotic complications.

From the Research

Significance of dRVVT

The significance of a dilute Russell viper venom time (dRVVT) of 42 seconds can be understood in the context of lupus anticoagulant detection.

• dRVVT is a test used to detect lupus anticoagulants, which are associated with an increased risk of thrombosis 2.
• A dRVVT result is typically considered positive if it is above a certain cutoff value, which may vary depending on the specific assay and laboratory 3.
• The clinical significance of a dRVVT result of 42 seconds would depend on the specific cutoff value used by the laboratory, as well as the patient's clinical history and other laboratory results 4, 5, 6.

Comparison of dRVVT Assays

Different dRVVT assays may have varying degrees of sensitivity and specificity for detecting lupus anticoagulants.

• Some studies have compared the performance of different dRVVT assays, including the detection of lupus anticoagulants in patients with thrombosis 2, 4, 6.
• The results of these studies suggest that dRVVT assays can be useful for detecting lupus anticoagulants, but the choice of assay and interpretation of results may depend on the specific clinical context 3, 5.

Interpretation of dRVVT Results

The interpretation of dRVVT results requires careful consideration of the patient's clinical history and other laboratory results.

• A positive dRVVT result may indicate the presence of lupus anticoagulants, but it is essential to confirm the result using additional testing, such as mixing studies and confirmatory assays 3.
• The results of dRVVT testing should be interpreted in the context of the patient's overall clinical picture, including their risk factors for thrombosis and other laboratory results 2, 4, 5, 6.