From the Guidelines
An elevated Partial Thromboplastin Time (PTT) Lupus Anticoagulant (LA) in a lupus panel indicates the presence of lupus anticoagulant antibodies, which increase the risk of blood clots, suggesting antiphospholipid syndrome (APS). This finding is based on the most recent guidelines for lupus anticoagulant detection, which emphasize the importance of combining two phospholipid-dependent clotting assays for accurate diagnosis 1. The presence of lupus anticoagulant antibodies can lead to an increased risk of thrombosis, and patients with this finding require further confirmatory testing, including a mixing study and more specific tests like the dilute Russell's viper venom time (dRVVT) or hexagonal phase phospholipid neutralization assay. Some key points to consider in the diagnosis and management of lupus anticoagulant include:
- The use of a combination of two phospholipid-dependent clotting assays for accurate diagnosis 1
- The importance of distinguishing between isolated lupus anticoagulant and lupus anticoagulant associated with positivity in ELISA tests, as the risk of thrombosis may vary 1
- The need for further confirmatory testing, including a mixing study and more specific tests like the dilute Russell's viper venom time (dRVVT) or hexagonal phase phospholipid neutralization assay
- The potential for anticoagulation therapy, typically with warfarin (target INR 2-3) for venous thrombosis or combined antiplatelet and anticoagulant therapy for arterial thrombosis, if confirmed 1. It is also worth noting that the updated guidelines for lupus anticoagulant detection provide additional details and specifications for the detection of lupus anticoagulants, which can help improve diagnosis and management of antiphospholipid syndrome (APS) 1.
From the Research
Elevated PTT Lupus Anticoagulant in Lupus Panel
- An elevated Partial Thromboplastin Time (PTT) Lupus Anticoagulant (LA) in a lupus panel indicates the presence of an acquired antiphospholipid antibody that can increase the risk of thromboembolism 2.
- This antibody can prolong the clotting time of in-vitro laboratory tests by binding phospholipid in the test system, leading to an increased risk of venous and arterial thrombosis, but not hemorrhage 3.
- The presence of LA is detected by laboratory testing, with the activated partial thromboplastin time and dilute Russell's viper venom time being the most commonly used tests 4.
- An elevated PTT in patients with LA can be associated with an increased risk of thromboembolic complications, despite the prolonged PTT suggesting a bleeding tendency 5.
Interference with Anticoagulant Therapy
- Anticoagulants can interfere with LA testing, leading to false-negative or false-positive results, and strategies such as avoidance of testing while patients are on anticoagulants, temporarily switching to an anticoagulant with less assay interference, or using anticoagulant neutralizers can mitigate these interferences 4.
- The use of a sensitive and an insensitive APTT reagent can provide a rapid screen for LA and discriminate between the presence of LA, heparin, and oral anticoagulants 6.
Clinical Implications
- Patients with LA are at increased risk of thromboembolic events, and anticoagulant therapy may be necessary to prevent these complications 2, 3.
- Monitoring anticoagulant effect with activated PTT can be unreliable in patients with a baseline elevated activated PTT, and alternative methods such as heparin levels or Factor X levels may be necessary 2, 3.