- •The current ISTH-SSC guidelines for LA testing aim to harmonize practices.
- •However, methodologies are not always consistent and alternatives are possible.
- •The impact of the cut-off value used and the way to normalize ratios remained limited.
- •It is important to understand the mixing test characteristics.
The ISTH-SSC guidelines for lupus anticoagulant (LA) testing recommend using in-house determined cut-off values, pooled normal plasma (PNP) for ratio normalization, and a ratio for the mixing test interpretation. They strongly support the mixing step role in the diagnostic process.
To investigate and compare the LA testing results and interpretations obtained following the ISTH-SSC guidelines or the available alternatives.
Blood samples for LA testing from 462 consecutive patients were evaluated for screening, mixing and confirmatory tests. The analysis focused on the interpretation differences between using (1) the in-house cut-off values versus the manufacturer's cut-off values, (2) a normalized ratio calculated using PNP at each run versus the mean of the reference interval, (3) a normalized ratio versus the index of circulating anticoagulant to interpret the mixing step, and (4) a two-step versus three-step procedure.
LA testing outcomes were comparable when using the in-house and manufacturer's cut-off values. More positive dilute Russell's viper venom (DRVV) time results were obtained with the normalized ratio based on PNP than with the mean of the reference interval. Overall, the mixing test results obtained with the normalized ratio and the index of circulating anticoagulant showed a good agreement. Among the 97 DRVV Screen test-positive samples, 33 and 89 were classified as LA-positive with the 3-step and the 2-step procedure, respectively.
The cut-off value used and the way to normalize ratios had a limited impact. Conversely, it is important to understand the mixing test characteristics to maximize its diagnostic potential.
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- International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS).J. Thromb. Haemost. 2006; 4: 295-306
- Pathogenesis of antiphospholipid syndrome: understanding the antibodies.Nat. Rev. Rheumatol. 2011; 7: 330-339
- Subcommittee on lupus Anticoagulant/Antiphospholipid antibodies. Laboratory criteria for antiphospholipid syndrome: communication from the SSC of the ISTH.J. Thromb. Haemost. 2018; 16: 809-813
- Update of the guidelines for lupus anticoagulant detection. Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis.J. Thromb. Haemost. 2009; 7: 1737-1740
- International Society for Thrombosis and Haemostasis Scientific and standardization Committee for Lupus Anticoagulant/Antiphospholipid antibodies. Clinical and laboratory practice for lupus anticoagulant testing: an International Society of Thrombosis and Haemostasis Scientific and standardization committee survey.J. Thromb. Haemost. 2019; 17: 1715-1732
- Guidance from the scientific and standardization committee for lupus anticoagulant/antiphospholipid antibodies of the international society on thrombosis and haemostasis: update of the guidelines for lupus anticoagulant detection and interpretation.J. Thromb. Haemost. 2020; 18: 2828-2839
- Recherche d’une thrombophilie biologique : propositions du GFHT 2020.Rev. Francoph. Hémostase Thrombose. 2020; 2: 93-126
- Laboratory Testing for the Lupus Anticoagulant: Approved Guideline; CLSI Document H60-A.Clinical and Laboratory Standards Institute, Wayne, PA, USA2014
- British Committee for Standards in haematology. Guidelines on the investigation and management of antiphospholipid syndrome.Br. J. Haematol. 2012; 157: 47-58
- Refinement of the cutoff values of the HemosIL AcuStar assay for the detection of anticardiolipin and anti–beta2 glycoprotein-1 antibodies.J. Thromb. Haemost. 2014; 12: 2034-2037
- Antiphospholipid antibody testing and standardization.Int. J. Lab. Hematol. 2014; 36: 352-363
- Variability of cut-off values for the detection of lupus anticoagulants: results of an international multicenter multiplatform study.J. Thromb. Haemost. 2017; 15: 1180-1190
- Lupus anticoagulant assay cut-offs vary between reagents even when derived from a common set of normal donor plasmas.J. Thromb. Haemost. 2020; 18: 439-444
- Lupus anticoagulant detection: out of control?.Int. J. Lab. Hematol. 2013; 35: 128-136
- Differences in lupus anticoagulant final conclusion through clotting time or rosner index for mixing test interpretation.Clin. Chem. Lab. Med. 2016; 54: 1511-1516
- Mixing test specific cut-off is more sensitive at detecting lupus anticoagulants than index of circulating anticoagulant.Thromb. Res. 2016; 139: 98-101
- Laboratory testing for lupus anticoagulants: a review of issues affecting results.Clin. Chem. 2007; 53: 1629-1635
- New guidelines for lupus anticoagulant: sensitivity and specificity of cut-off values calculated with plasmas from healthy controls in mixing and confirmatory tests: NEW LA LABORATORY CRITERIA.Int. J. Lab. Hematol. 2012; 34: 208-213
- Mixing studies in lupus anticoagulant testing are required at least in some type of samples.J. Thromb. Haemost. 2015; 13: 1475-1478
- No more mixing tests required for integrated assay systems in the laboratory diagnosis of lupus anticoagulants?.J. Thromb. Haemost. 2010; 8: 1120-1122
- Laboratory investigation of lupus anticoagulants: mixing studies are sometimes required.J. Thromb. Haemost. 2010; : 2828-2831
- Lupus anticoagulant testing–sometimes mixing is required: potential for false negatives without mixing studies.Blood Coagul. Fibrinolysis. 2013; 24: 673-676
- Optimisation of lupus anticoagulant tests: should test samples always be mixed with normal plasma?.Thromb. Haemost. 2014; 112: 736-742
- Lupus anticoagulant testing and anticoagulation do not mix: quantitation of discrepant results and potential approaches to reduce false positives.Br. J. Haematol. 2014; 167: 704-707
- Mixing studies for lupus anticoagulant: mostly no, sometimes yes.Clin. Chem. Lab. Med. 2020; 58: 492-495
- Mixing studies for lupus anticoagulant: mostly yes, sometimes no.Clin. Chem. Lab. Med. 2020; 58: 487-491
- Interpretation of normal plasma mixing studies in the laboratory diagnosis of lupus anticoagulants.Thromb. Res. 2007; 119: 369-376
- Guidelines on the investigation and management of antiphospholipid syndrome.Br. J. Haematol. 2012; 157: 47-58
- Clinical significance of the mixing test in laboratory diagnoses of lupus anticoagulant: the fate of the mixing test in integrated lupus anticoagulant test systems.Blood Coagul. Fibrinolysis. 2012; 23: 739-744
- Normal plasma mixing studies in the laboratory diagnosis of lupus anticoagulant.J. Thromb. Haemost. 2003; 1: 2689-2691
- The dilution effect of equal volume mixing studies compromises confirmation of inhibition by lupus anticoagulants even when mixture specific reference ranges are applied.Thromb. Res. 2006; 118: 523-528
- The sensitivity and specificity of commercial reagents for the detection of lupus anticoagulant show marked differences in performance between photo-optical and mechanical coagulometers.Thromb. Haemost. 1999; 81: 758-762
- Comparison of six dilute Russell viper venom time lupus anticoagulant Screen/Confirm assay kits.Semin. Thromb. Hemost. 2013; 39: 315-319
Published online: February 17, 2023
Accepted: February 14, 2023
Received in revised form: February 10, 2023
Received: November 7, 2022
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