Background: The prothrombin time (PT) is widely used to screen single or combined deficiencies of the extrinsic coagulation pathway and to monitor vitamin K antagonist (VKA) anticoagulant therapy. The (h)PT-Phen™ LRT reagent (HYPHEN BioMed, Neuville-sur-Oise, France) is a new liquid, ready to use thromboplastin reagent containing human recombinant tissue factor for the determination of PT on citrated human plasma. However, data on both its analytical performance and its use in current practice are scarce.

Aims: To assess the analytical performances of the (h)PT-Phen™ LRT and to compare this reagent with a widely used routine PT reagent (Neoplastine® CI Plus, Stago, France).

Methods: Analytical performances of the (h)PT-Phen™ LRT reagent were assessed on a CN-6000 analyzer (Sysmex Corp., Japan). Blood samples from 120 healthy volunteers were collected to generate reference-values. PT was further determined in plasma samples from 84 patients treated with VKA, 28 patients suffering from hepatic failure, and 35 patients with low levels of factor V with the (h)PT-Phen™ LRT and with the Neoplastine® CI Plus reagent on CN-6000 and STA-R Max 2® analyzers, respectively.

Results: Figure 1 : PT or INR values in healthy volunteers (A), in patients with hepatic failure and known factors V low levels (B), and in patients treated with vitamin K antagonist (C).A good open-vial on-board stability over 14 days was observed. Excellent repeatability and intermediate precision measurements were obtained (CV<1.6%). Significant correlations were observed between the 2 reagents in normal subjects (r= 0.76, p<0.0001, Figure 1 A) and in those with hepatic failure and known factors V low levels (r=0.69, p<0.0001, Figure 1B). There was a good agreement between methods in samples from patients receiving VKA and no significant differences between methods with increasing INR values (Figure 1C).

Conclusions: In light of its excellent analytical performance and its good agreement with a relevant comparator reagent, the (h)PT-Phen™ LRT appears as suitable for routine use to detect factor II, V, VII and X deficiency and to monitor VKA in laboratories with high sample throughput.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/evaluation-of-a-new-thromboplastin-reagent-containing-human-recombinant-tissue-factor-for-the-determination-of-prothrombin-time-reagent-the-hpt-phen-lrt/