Testing for antiphospholipid antibodies: Advances and best practices

Abstract

The diagnosis of antiphospholipid syndrome (APS) relies on the detection of circulating antiphospholipid antibodies (aPL). Currently, lupus anticoagulant (LAC), anticardiolipin (aCL), and antibeta2-glycoprotein I antibodies (aβ2GPI) IgG or IgM are included as laboratory criteria if persistently present. Progress has been made on the standardization of tests as guidelines on LAC testing and immunological assays for aCL and aβ2GPI are published. However, LAC measurement remains a complicated procedure with many pitfalls and interfered by anticoagulant therapy. Solid-phase assays for aCL and aβ2GPI still show interassay differences. These methodological issues make the laboratory diagnosis of APS challenging. In the interpretation of aPL results, antibody profiles help in identifying patients at risk. Noncriteria aPL, such as antibodies against the domain I of beta2-glycoprotein (aDI) and antiphosphatidylserine-prothrombin (aPS/PT) antibodies have been studied in the last years and may be useful in risk stratification of APS patients. But, aDI and aPS/PT are not included in the current diagnostic criteria and testing in daily practice is not recommended as these antibodies have no added value in the diagnosis of APS. This review will focus on the technical aspects of the laboratory methods, the clinical relevance of assays and interpretation of aPL results in the diagnosis of APS. K E Y W O R D S anticardiolipin antibodies, antiphospholipid syndrome, anti-β2 glycoprotein I antibodies, guidelines, lupus anticoagulant

Systematic Review of Antiphospholipid Antibodies in COVID-19 Patients: Culprits or Bystanders?

“…Some studies have found a high prevalence of aPL [ 6 •, 18 , 23 , 37 , 43 , 57 ] while others found a low prevalence and this could be linked to disease severity [ 19 , 24 , 26 , 35 •, 42 , 45 , 55 ]. Xiao et al found aPL in 31 out of 66 patients requiring ICU admission but not in patients with noncritical conditions [ 45 ].…”

“…The main reason is probably linked to aPL tests and the interpretation of the results. Assays may be affected by several analytical factors, including methodological issues due to the heterogeneity of aPL, different tests from one laboratory to another, and pre-analytical factors due to the clinical condition of the patient in whom the assay is performed [ 57 ]. In particular inflammation may cause false positive determination of LA [ 66 – 68 ].…”

Laboratory Approaches to Test the Function of Antiphospholipid Antibodies

“…The general approach is to test the anti-β 2 GPI and the anti-CL antibodies both for IgG and IgM autoantibodies, and it was concluded that there is no strong evidence suggesting that IgA isotypes provide additional information except in rare cases. [33][34][35] Undoubtedly, the strongest predictor is IgG, and more recent data also question the general usefulness of the IgM aPLs 36,37 and on the other hand there is also evidence that the anti-β 2 GPI IgA significantly adds to the evaluation of thrombotic risk (e.g., in SLE). 38 To avoid transient autoantibodies, measurements should be performed two times, 12 weeks apart.…”

Current Promising Biomarkers and Methods in the Diagnostics of Antiphospholipid Syndrome: A Review

“…The significance of aCL IgA for the development of thrombotic complications has also been of much interest recently [47]. Using CLIA (cut-off recommended by the manufacturer >20 CU), Liu et al detected aCL IgA in 192 samples of APS in 42%, in 90 samples of seronegative APS (SN-APS) in 12%, and in healthy donors in 0% [24].…”

“…The LA results are interpreted according to ISTH SSC as positive/negative based on the normalized ratio (NR) calculation (NR = patient/polled normal plasma (PNP)) [69]. With regard to the use of different analyzers and reagents, each laboratory should determine its own cut-off for LA (99th percentile) by measuring ideally 120 (minimally 40) healthy controls [47,70,71]. Cohen et al [72] carried out a survey in 575 laboratories by means of a "Lupus Program," the External quality Control of diagnostic Assay and Test Foundation (ECAT).…”