Activated protein C resistance test
(Redirected from
ETP-based activated protein C resistance test
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hypercoagulability | |
The activated protein C resistance (APCR) test is a
Methodology
The aPTT-based APC resistance test involves a modified aPTT test performed in the presence and absence of
endogenous thrombin potential (ETP; area under the thrombin generation curve).[5] The result is expressed as a normalized APC sensitivity ratio (nAPCsr), which corresponds to the ratio of the ETP measured in the presence and absence of APC divided by the same ratio in reference plasma.[5] nAPCsr values range from 0 to 10.[5] Opposite to the case of the APCsr with the aPTT-based APC resistance test, higher nAPCsr values indicate greater APC resistance.[5][8] This is the result of the fact that APC prolongs the aPTT but inhibits thrombin generation.[8]
Whereas the aPTT-based APC resistance test only measures the initiation phase of
prothrombin and factor VIII, whereas the ETP-based test is more sensitive to levels of tissue factor pathway inhibitor (TFPI) and protein S.[5] The ETP-based test has traditionally been performed using methods such as the calibrated automated thrombogram (CAT) and has been limitedly available due to its technical difficulty.[2] Recently however, a fully automated commercial test system called the ST Genesia has been introduced, and it has been said that this should allow for adoption of TGAs and ETP-based APC resistance tests in routine clinical settings.[2][12]
Influences
estetrol/drospirenone (E4/DRSP), ethinylestradiol/levonorgestrel (EE/LNG), ethinylestradiol/desogestrel (EE/DSG), and ethinylestradiol/drospirenone (EE/DRSP).[5]
History
The aPTT-based APC resistance test was developed in 1993, while the ETP-based test was developed in 1997.[5] For many years, the ETP-based APC resistance test suffered from a lack of standardization which hampered study-to-study comparison.[21] By 2020 however, a validated methodology was developed aiming to propose a standardized and harmonized scale for ETP-based APC resistance, the normalized activated protein C sensitivity ratio (nAPCsr).[21]
References
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