A-168 Comparison of Two Different Lupus Anticoagulant Hexagonal Phase Phospholipid Confirmatory Assays on an Automated Coagulation Analyzer

Abstract Background Antiphospholipid syndrome (aPS) is an autoimmune disorder resulting in venous and/or arterial thrombosis, characterized by presence of lupus anticoagulants (LA) in patient plasma, also referred to as antiphospholipid antibodies. Depending on clinical history and symptoms, or if an unexpected elevated routine aPTT result is observed, LA laboratory testing would be performed, if appropriate. According to published clinical guidelines, LA tests should use aPTT-based and dRVVT-based screening (low phospholipid) and confirmatory (high phospholipid) methods, run in parallel. aPS diagnosis is confirmed from both clinical and laboratory criteria. Laboratory criteria are met if either the aPTT or dRVVT confirmatory test results are positive, and if lab positivity is confirmed following repeated testing 12 weeks following initial results. Due to the multiple tests used, and different manufacturers’ reagents, analysis of comparative performance allows users to identify the optimal tests to use. Objectives of the study were 1) compare intra-run and total precision of two different aPTT-based LA confirmatory tests on a newly available automated coagulation instrument equipped with improved pipetting methodology and preanalytical sample integrity detection and 2) correlate results from the two different aPTT-based LA confirmatory test assays. Methods CRYOcheck Hex LA (Precision BioLogic, Inc., Dartmouth, NS, Canada) and Staclot LA (Diagnostica Stago, Inc., Parsippany, NJ, USA) were run on a STA R Max3 automated coagulation analyzer (Diagnostica Stago, Inc.), using manufacturer recommended protocols. For intra-run precision and total precision analysis, replicates of 5 quality control samples were used (STA Control LA 1+2, Diagnostica Stago, Inc.). For the correlation studies, 20 different LA positive samples were used, supplied by the Specimen Access Team (SAT) from Laboratory Corporation of America Holdings, Burlington, NC, USA. LA positivity was defined as positive by CRYOcheck Hex LA delta result > 11 seconds, which was the cutoff determined at LabCorp’s facility. CRYOcheck Normal Donor Set plasmas were used for normal samples (Precision BioLogic, Inc.). Samples were run in batches containing 5 normal samples and 5 abnormal samples, with quality control run at the beginning and end of each batch. Results Intra-run precision was superior for Staclot LA compared to CRYOcheck Hex LA, with the exception of the high phospholipid “LA Correct” positive tube from CRYOcheck Hex LA. Total precision was either comparable or superior for Staclot LA compared to CRYOcheck Hex LA. In addition, correlation data showed Staclot LA recovered the same result between 3 different aliquots of the same patient mother tube, whereas CRYOcheck Hex LA recovered varying results between runs, when using manufacturer recommended cutoffs. Conclusions Analysis of intra-run and total precision, along with result correlation and recovery between multiple sample aliquots is recommended for when coagulation laboratories evaluate different manufacturers’ reagents. Our data indicate Staclot LA demonstrates superior performance to the CRYOcheck Hex LA on the STA R Max3 automated coagulation analyzer.

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