The Russell viper venom time (RVVT) test for investigation of lupus anticoagulant (LA)

Abstract

Lupus anticoagulants (LAs) are a laboratory representation of the clinical syndrome of antiphospholipid syndrome (APS), and can also arise in other pathological states. Laboratory testing for LA is complex and three separate recent guidelines have been published. One test, the Russell viper venom time (RVVT), is the mandated laboratory test for inclusion in LA identification/exclusion in all three guidance documents. This is because the the RVVT is recognized to have great sensitivity for LA, with this generally recognized to be greater than that of most other LA screening assays. However, the RVVT is also very sensitive to the presence of many anticoagulant drugs, which diminishes its specificity for LA. Various strategies can be used to improve LA specificity and reduce anticoagulant assay interference.

Coagulation mixing studies: Utility, algorithmic strategies and limitations for lupus anticoagulant testing or follow up of abnormal coagulation tests

“…There are actually several methods available to interpret mixing studies as having either “corrected” (suggesting factor deficiency) vs “not corrected” (suggesting factor inhibitor) …”

“…There are of course many other potential options, especially for LA investigation . As another example, a more subjective approach is sometimes used.…”

“…For LA investigation, ratios of test results are instead sometimes used to identify the cut‐off. For example, a ratio of 1.2 is commonly applied to ratios to identify the absence of LA (value < 1.2) or presence of LA (value ≥ 1.2) . In essence, this is similar to using a value of 20% for correction.…”

“…LA represent a laboratory representation of the clinical syndrome of antiphospholipid syndrome (APS), and can also arise in other pathological states . For a more complete discussion of LA, the reader is referred to an earlier test of the month publication in this journal . Some mention of LA testing, mixing tests and alternate approaches has already been mentioned above.…”

“…It should also be acknowledged that laboratory testing for LA is complex, with three separate recent guidelines published . Of major relevance to the current review is the inclusion of mixing test in all three guidance documents, albeit with different emphasis around importance or placement in the LA diagnostic strategy in each publication . Workers in the field also differ in their opinions on whether confirmatory LA tests should be performed on neat (patient) test samples, and/or on test mixtures (patient/normal plasma).…”