Taipan snake venom time has high sensitivity for lupus anticoagulants in non-anticoagulated, triple positive antiphospholipid syndrome patients.

INTRODUCTION: Dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) are the mainstay assays in lupus anticoagulant (LA) detection yet they have limitations, particularly in relation to interferences and specificity. The recently validated Taipan snake venom time (TSVT) screening with ecarin time (ET) confirmatory assays overcome many of those limitations due to the innate specificity engendered from direct prothrombin activation, and insensitivity to the effects of vitamin K antagonists (VKA). The present study aimed to further evidence diagnostic utility of TSVT/ET by performing them in samples from 116 nonanticoagulated patients with established triple-positive antiphospholipid syndrome (APS). METHODS: Samples were identified in three expert centres who performed dRVVT, APTT and solid phase antiphospholipid antibody assays with reagents from a variety of manufacturers. All samples additionally received TSVT/ET analysis using standardised reagents. RESULTS: Ninety seven of 116 (83.6%) were dRVVT- and APTT-positive, 85/97 (87.6%) of which were TSVT/ET-positive, 9/116 (7.8%) were dRVVT-positive only, 6 of which were TSVT/ET-positive, and 10/116 (8.6%) were APTT-positive only, 5 of which were TSVT/ET-positive. 96/116 TSVT/ET-positivity returned a high sensitivity for LA of 82.8%. Low coefficients of determination revealed weak relationships between LA potency and anticardiolipin and anti-ß2-glycoprotein I antibody titres for all three LA assays. CONCLUSIONS: TSVT/ET has high sensitivity for the clinically significant LA found in triple positive APS patients. TSVT/ET can establish multiple LA assay positivity in nonanticoagulated patients negative for one of dRVVT or APTT, and is the only assay pairing insensitive to VKAs, the recommended anticoagulation for APS.

Triple-positive antiphospholipid syndrome does not guarantee positivity in each lupus anticoagulant assay.

BACKGROUND: Triple positivity for all 3 criteria antiphospholipid antibodies confers high risk of symptom development in carriers, and recurrence in antiphospholipid syndrome (APS). Most triple-positivity studies report lupus anticoagulant (LA) testing as positive without distinguishing between positivity with dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) and single-assay positivity or only perform dRVVT. Single LA assay repertoires remain in use in some centers, which risks missing some triple positives. Positivity with both assays may identify higher risk. OBJECTIVES: The aim of this study is to investigate the frequency of single LA assay positivity in triple-positive patients. METHODS: Three hundred forty-two triple-positive profiles from nonanticoagulated patients (237 APS, 45 systemic lupus erythematosus without APS symptoms, and 60 nonclinical criteria) were identified from laboratory databases and assessed for LA positivity by dRVVT and/or APTT. RESULTS: Seventy-three of 237 (30.8%) APS samples were LA-positive with 1 assay, 40/237 (16.9%) by dRVVT only, and 33/237 (13.9%) with APTT only. Nineteen of 45 (42.2%) were LA-positive with 1 assay in the systemic lupus erythematosus cohort; 12/45 (26.7%) with dRVVT only and 7/45 (15.5%) with APTT only. Thirty-three of 60 (55.0%) were LA-positive with 1 assay in the nonclinical criteria cohort; 24/60 (40.0%) with dRVVT only and 9/60 (15.0%) with APTT only. The most common solid-phase assay profile was elevated immunoglobulin G aCL and aß2GPI. CONCLUSION: Up to 55.0% of triple-positive samples were positive in 1 LA assay, representing significant potential for misdiagnosis and inappropriate management via single LA assay repertoires.