A study is presented which assesses the diagnostic impact of incorporating Taipan snake venom time (TSVT) with ecarin time confirmatory test into an existing dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) repertoire when testing nonanticoagulated patients for lupus anticoagulants. A total of 387 plasma samples from nonanticoagulated patients being investigated for antiphospholipid antibodies were tested for lupus anticoagulant by dRVVT and dilute APTT with confirmatory and mixing tests, and TSVT with ecarin time, with commercially available reagents. All were analyzed on a Sysmex CS2000i automated analyzer. Lupus anticoagulant was not detected by dRVVT, dilute APTT or TSVT screening in 265 of 387 (68.5%) samples. A lupus anticoagulant was detected in 60 (15.5%) samples in dRVVT and/or dilute APTT analysis, but gave normal TSVT ratios. Thirty-nine (10.1%) were positive by TSVT and ecarin time and one or both of dRVVT and dilute APTT testing, whereas a further 23 (5.9%) were only positive in TSVT/ecarin time testing. Most of the lupus anticoagulants manifested in dRVVT and/or APTT analysis, as might be anticipated for this reagent pairing. The samples positive by TSVT/ecarin time only, as has been previously demonstrated, emphasize that the many variables that impact lupus anticoagulant testing mean that even a well established dRVVT and APTT pairing cannot deliver diagnostic certainty. Interference by direct factor Xa inhibitors in dRVVT testing could pave the way for wider adoption of TSVT screening as we gain more evidence of its diagnostic performance.

Although platelet integrity and PDGF-BB fell over time, the intermittently agitated non-oxygen permeable container appeared to retain better platelet integrity and function, and PDGF-BB release, than other storage conditions, with potential for clinical use for 5-8 days.

BackgroundGold standard lupus anticoagulant (LA) assays and reference plasmas do not exist and detection is based on inference in a medley of coagulation assays, creating potential for interpretive discrepancies when applying different algorithms.ObjectivesTo investigate discrepancies from applying different algorithms to a common data set.MethodsDiagnostic data on 311 non‐anticoagulated patients LA‐positive by dilute Russell's viper venom time (dRVVT) and/or dilute activated partial thromboplastin time (dAPTT) assays were employed to compare algorithms. Routine testing applied interpretive criteria from guidelines endorsing classification as LA‐positive despite negative mixing tests, after exclusion of other clotting abnormalities. Integrated testing without mixing tests, and the classical algorithm where negative mixing tests preclude confirm tests, were then retrospectively applied to those data.ResultsInitial testing showed 92/311 (29.6%) were LA‐positive by dRVVT only, 156/311 (50.1%) by dAPTT only, and 63/311 (20.3%) by both assays. All dAPTT‐positive plasmas remained positive with integrated testing but eight dRVVT‐positives became negative. Other data suggested they were false‐negatives. The classical algorithm altered 52/155 (33.5%) dRVVT and 111/219 (50.7%) dAPTT interpretations to LA‐negative because of normal mixing tests, most of which were apparently weak LA in undiluted plasma.ConclusionsThe classical algorithm improves diagnostic specificity and confidence but risks missing some genuine LA due to false‐negative mixing tests. Integrated testing can be diagnostically accurate and logistically efficient but oversimplifies complex cases. Performing mix and confirm in response to an elevated screen with their interpretation based on clinical data, coagulation screens and the LA‐assay design offers a potentially valuable option.

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