Abstract Number: PB0382
Meeting: ISTH 2021 Congress
Background: The mixing test is considered useful for lupus anticoagulant (LA) diagnosis and is also recommended to differentiate between acquired hemophilia A (AHA) and factor deficiency. In our previous study, we proposed the mixing test formula using index of circulating anticoagulant (ICA) calculated from the clotting times of without incubation and 2 hours incubation.
Aims: Recently, we have developed new APTT reagent prepared from ellagic acid as the activator and synthetic phospholipids. The purpose of this study was to validate the mixing test formula proposed in our previous study in that reagent.
Methods: We examined total 100 clinical samples including 37 LA-positive, 4 factor deficiency, 51 anticoagulant drugs and 9 FVIII inhibitor. ICA values, calculated from the clotting times without incubation and after 2 hours incubation, were defined as ICA immediate (ICAi) and ICA delated (ICAd), respectively. ICAd/ICAi and ICAd – ICAi were calculated as the mixing test formula. 132% and 6.4 established previously were used as the cut-off values in new APTT reagent for the validation, respectively.
Results: The ICAi values of LA-positive samples were significantly higher than those in another samples, and FVIII inhibitors samples as well as LA-positive showed the elevated ICAd values than those of factor deficiency and anticoagulant drugs samples. In ICAd/ICAi and ICAd – ICAi formulas, only FVIII inhibitor samples were elevated, and the sensitivity and specificity for FVIII inhibitor were 100% and 79.3% for ICA/ICAi and 100% and 94.6% for ICAd – ICAi, respectively.
Conclusions: ICAd/ICAi and ICAd – ICAi showed significantly higher values in FVIII inhibitor and acceptable sensitivity and specificity. It was confirmed that these formulas were worked well in new APTT reagent. These formulas were useful for the discrimination between LA and FVIII inhibitor and can contribute to the rapid diagnosis and treatment.
To cite this abstract in AMA style:Kumano O, Shimomura D, Kitano K, Arai N, TM. Validation of Mixing Test Formula for the Discrimination between Lupus Anticoagulant and Acquired Hemophilia A in New APTT Reagent [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/validation-of-mixing-test-formula-for-the-discrimination-between-lupus-anticoagulant-and-acquired-hemophilia-a-in-new-aptt-reagent/. Accessed December 5, 2021.
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