Screening for Lupus anticoagulant has become easily accessible to labs across the world.
Since the inception of the Dilute Russell Viper Venom Time (dRVVT) by Thiagarajan et al in 1986, screening for Lupus anticoagulant has become easily accessible to labs across the world. This landmark paper expertly demonstrates the method development of the dRVVT screen and the theory behind its fundamental principles.
The dRVVT test was developed in response to the low specificity shown by the combined use of the Activated Partial Thromboplastin Time (APTT) and Tissue Thromboplastin Inhibition test (TTI) as a screen for the detection of lupus anticoagulants.
A prolonged APTT that does not correct with the addition of normal plasma and an extended TTI time were historically used to identify a Lupus anticoagulant. False positive results when using TTI clotting times are common due to antibodies specific to factors VIII, IX or XI.
In addition to this some Lupus anticoagulants do not prolong the TTI time. This therefore characterises the need for a test with a higher specificity for Lupus anticoagulant.
The dRVVT test increases specificity for Lupus anticoagulant by using variable phospholipids concentration as a benchmark for differentiating inhibitors.
As Lupus anticoagulant is immunologically active towards anionic phospholipids, high concentrations will normalise the dRVVT clotting time; this is not the case with factor antibodies.
Extension of the dRVVT clotting time can be achieved by reducing the level of phospholipid to the minimum necessary for prothrombin activation.
It can therefore be demonstrated that phospholipid dependent normalisation of the dRVVT time is specific to Lupus anticoagulant.
Blood Journal (external site)
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