Abstract Number: PB1064
Meeting: ISTH 2021 Congress
Background: Mixing studies in lupus anticoagulant (LA) testing are used to discriminate between LA and factor deficiencies or the presence of other inhibitors. Anticoagulants have been identified with capabilities to enhance LA mixing study sensitivities.
Aims: This study investigates automated LA mixing study solutions with enhanced sensitivities to avoid misclassification of weak LA samples.
Methods: Anticoagulants that greatly enhance LA positive sample test ratio but with minimum impact on LA negative sample test ratio were identified and added to platelet poor normal plasma (PPP-AC). dRVVT screen and confirm tests were modified to include a mixing step of LA samples with PPP-AC.
Results: As shown in Figure 1, for mixing studies that do not require incubation at 37°C, d-phenylalanyl-1-prolyl-1-arginine-chloromethyl ketone in PPP (PPP-PPACK) significantly increased the dRVVT screen/confirm (S/C) ratio of an LA positive sample while slightly decreasing the S/C ratio of an LA negative sample, leading to an increase of test ratio from 1.38 to 1.74 in the 1:1 mixing study for an LA positive sample with a test ratio of 1.67.
In the presence of inhibitors that require incubation at 37°C as shown in Figure 2, the impact of hirudin in PPP (PPP-Hirudin) on dRVVT S/C ratio was considerably stronger for a LA positive sample than for a LA negative sample. Thus, the test ratio was greatly improved. A 1:1 mixture of LA negative sample with PPP-Hirudin may be used to normalize the test ratio.
Conclusions: Particular anticoagulants have demonstrated unique impact on dRVVT results. Specifically, PPP-PPACK provides a simple automated mixing study solution with enhanced sensitivity to LA positive samples when incubation at 37°C is not needed. PPP-Hirudin, on the other hand, is useful for mixing studies that require incubation.
To cite this abstract in AMA style:Cao Z, Bottenus R, Kung C. Automated Methods for the Enhancement of Lupus Anticoagulant Mixing Study Sensitivities [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/automated-methods-for-the-enhancement-of-lupus-anticoagulant-mixing-study-sensitivities/. Accessed February 28, 2024.
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