From the Guidelines
A prolonged Activated Partial Thromboplastin Time (APTT) of 38 seconds is indicative of potential lupus anticoagulant sensitivity, requiring further investigation with confirmatory testing to assess the risk of thrombosis and guide management. This finding suggests the possible presence of lupus anticoagulant antibodies, which are associated with an increased risk of thrombosis rather than bleeding 1. The patient should undergo a mixing study followed by more specific tests like the dilute Russell viper venom time (dRVVT) or hexagonal phase phospholipid neutralization assay to confirm the presence of lupus anticoagulant antibodies. If confirmed, the patient should be evaluated for antiphospholipid syndrome, especially if they have a history of unexplained blood clots, recurrent pregnancy losses, or autoimmune disorders like systemic lupus erythematosus 1. Management depends on clinical context, with patients with thrombotic events typically requiring anticoagulation therapy, such as warfarin with an INR target of 2-3, or in some cases direct oral anticoagulants, while asymptomatic individuals with no history of clots may simply need monitoring. Key considerations in management include:
- The use of warfarin with a target INR of 2-3 for patients with venous thrombosis 1
- The potential need for high-intensity anticoagulation (target INR 3.0-4.0) in patients with arterial or recurrent thrombosis 1
- The importance of repeat testing in 12 weeks to confirm persistence of the antibody, as lupus anticoagulant can sometimes be transiently positive during infections or with certain medications. Overall, the presence of lupus anticoagulant sensitivity, as indicated by a prolonged APTT, requires careful evaluation and management to mitigate the risk of thrombosis and improve patient outcomes.
From the Research
Significance of Prolonged Activated Partial Thromboplastin Time (APTT)
- A prolonged APTT of 38 seconds can be indicative of Lupus Anticoagulant (LA) sensitivity, which is associated with an increased risk of thrombosis 2.
- LA can cause aPTT prolongation, and in rare cases, it can lead to bleeding tendency, especially when combined with other hemostasis abnormalities 3.
- The presence of LA can interfere with the measurement of prothrombin time (PT) and international normalized ratio (INR), leading to inaccurate results 4, 5.
Clinical Implications
- Patients with LA are at an increased risk of thrombotic events, and the risk is further increased by the presence of cardiovascular risk factors such as diabetes and active smoking 2.
- The use of warfarin therapy in patients with LA can be complicated by the interference of LA with PT and INR measurements, and alternative approaches to monitoring warfarin therapy may be necessary 4, 5.
- A prolonged lupus-sensitive APTT can be used as a risk factor for thrombotic events in patients with LA, and it can help stratify patients into subgroups with different risks of thrombosis 2.
Diagnostic Approaches
- The lupus-sensitive PTT-LA can be used as a screening test for LA, and calculating a ratio between the PTT-LA and a less sensitive APTT reagent can improve the performance of the test 6.
- Other diagnostic approaches, such as mixing studies and diluted Russell's viper venom confirmation test, can be used to confirm the presence of LA 6.