Abstract Number: PB0372
Meeting: ISTH 2021 Congress
Background: Lupus anticoagulant (LA) testing is essential for diagnosing antiphospholipid syndrome (APS) for which lifelong anticoagulant therapy is often indicated. The test is commonly ordered for patients with a history of thrombosis, recurrent spontaneous fetal loss and pre-operative patients with prolonged PTT. The current LA testing algorithm at our institution includes PTTLA; manual hexagonal (II) phase phospholipid neutralization (HPPN) assay and dilute Russell Viper Venom time (dRVVT) in addition to screening PT, aPTT and TT. The manual HPPN assay had high CV and low reproducibility in our laboratory. The silica clotting time (SCT) can be an automated alternative to PTTLA-HPPN assay.
Aims: To evaluate the concordance and reproducibility of automated SCT and PTTLA-HPPN assay.
Methods: Consecutive patient specimens were tested over a 2-month period following current LA algorithm plus SCT. Automated coagulation tests were performed on ACL TOP 700 analyzer. The HPPN assay was performed on manual hemostasis analyzer. The cutoffs for positives were obtained from 20 normal donor specimens. Reproducibility for SCT and HPPN were assessed from 8 reactive samples.
Results: 263 specimens were analyzed for comparison between PTTLA-HPPN and SCT. The SCT normalized ratio, PTTLA and HPPN assay positive test cut-off values were 1.21, 43.0 seconds and 8.0 seconds, respectively. Both SCT and PTTLA-HPPN assay were negative in 249 specimens, and both were positive in 3 specimens. In total, 252 results were concordant, and the overall percent agreement was 95.8%. Positive percent agreement and negative percent agreement were 37.5% and 97.6%, respectively. CV for HPPN assay ranged from 14.1% to 86.2% (Median: 41.3%); CV for SCT ranged from 1.1% to 25.7% (Median: 5.3%).
Conclusions: LA negative results from SCT showed good agreement with PTTLA-HPPN, while discrepancies were found with some positive LA results. The SCT reproducibility was high with 5.3% median CV.
To cite this abstract in AMA style:Gao XT, Sumugod R, Carmichael K, Lindholm P, Gillard L, Lerret N. Evaluation of Silica Clotting Time and Hexagonal (II) Phase Phospholipid Neutralization for Lupus Anticoagulant Detection [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/evaluation-of-silica-clotting-time-and-hexagonal-ii-phase-phospholipid-neutralization-for-lupus-anticoagulant-detection/. Accessed November 29, 2023.
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