Antiphospholipid antibodies detected by line immunoassay differentiate among patients with antiphospholipid syndrome, with infections and asymptomatic carriers

Abstract

BackgroundAntiphospholipid antibodies (aPL) can be detected in asymptomatic carriers and infectious patients. The aim was to investigate whether a novel line immunoassay (LIA) differentiates between antiphospholipid syndrome (APS) and asymptomatic aPL+ carriers or patients with infectious diseases (infectious diseases controls (IDC)).MethodsSixty-one patients with APS (56 primary, 22/56 with obstetric events only, and 5 secondary), 146 controls including 24 aPL+ asymptomatic carriers and 73 IDC were tested on a novel hydrophobic solid phase coated with cardiolipin (CL), phosphatic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, beta2-glycoprotein I (β2GPI), prothrombin, and annexin V. Samples were also tested by anti-CL and anti-β2GPI ELISAs and for lupus anticoagulant activity. Human monoclonal antibodies (humoAbs) against human β2GPI or PL alone were tested on the same LIA substrates in the absence or presence of human serum, purified human β2GPI or after CL-micelle absorption.ResultsComparison of LIA with the aPL-classification assays revealed good agreement for IgG/IgM aß2GPI and aCL. Anti-CL and anti-ß2GPI IgG/IgM reactivity assessed by LIA was significantly higher in patients with APS versus healthy controls and IDCs, as detected by ELISA. IgG binding to CL and ß2GPI in the LIA was significantly lower in aPL+ carriers and Venereal Disease Research Laboratory test (VDRL) + samples than in patients with APS. HumoAb against domain 1 recognized β2GPI bound to the LIA-matrix and in anionic phospholipid (PL) complexes. Absorption with CL micelles abolished the reactivity of a PL-specific humoAb but did not affect the binding of anti-β2GPI humoAbs.ConclusionsThe LIA and ELISA have good agreement in detecting aPL in APS, but the LIA differentiates patients with APS from infectious patients and asymptomatic carriers, likely through the exposure of domain 1.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1018-x) contains supplementary material, which is available to authorized users.

Profiles of criteria and non-criteria anti-phospholipid autoantibodies are associated with clinical phenotypes of the antiphospholipid syndrome

“…Last but not least, from the diagnostic perspective, the LIA was easy, efficient and with good sensitivity and specificity while employing cutoffs ascertained by healthy controls. This method enabled the discrimination of aPL found in APS patients from those in asymptomatic carriers as reported previously 24 .Within our controls, some aPLs were numerically more prevalent among septic control patients compared to healthy subjects, but a significant difference was observed only for anti-β2GP1 IgG. The latter transient appearance during infection was formerly reported 49,50 .…”

“…Lately, a new technique for aPLs testing was developed, using a line immunoassay (LIA), a multiplex method that permits estimation of a relatively large profile of aPLs concomitantly 6,22 . This novel assay technique appears to discriminate aPLs associated with APS from aPLs detected during infectious diseases and even asymptomatic carriers and may detect specific binding of aβ2GP1 to domain 1 (D1) of the β2GP1 16,[23][24][25] .…”

Prevalence and Thrombotic Risk Assessment of Anti-β2 Glycoprotein I Domain I Antibodies: A Systematic Review

“…A total of 13 studies, [20][21][22][23][24][25][26][27][28][29][30][31][32] including a total of 6,169 patients (comprising a total of 533 patients with APS and 68 with systemic lupus erythematosus [SLE]), which included testing of anti-β 2 GPI-DI antibodies in diverse cohorts of patients, were excluded from the analysis of prevalence. The exclusion of these studies was based on (1) the impossibility of extrapolating clinical or laboratory data, in particular when reporting the results of anti-β 2 GPI-DI positivity, 23,26 (2) lack of reported data on anti-β 2 GPI-DI prevalence, 25 (3) no defined cutoffs of positivity, 27 and/or (4) testing results expressed only in relation to the control groups.…”

The Significance of Antibodies against Domain I of Beta-2 Glycoprotein I in Antiphospholipid Syndrome

“…44 In agreement with these results, a line immunoassay was able to discriminate patients with APS from infectious patients and asymptomatic carriers, likely through the way β 2 GPI is oriented on the matrix, resulting in the exposure of domain I. 45 Apart from these full-length β 2 GPI assays, specific assays for the detection of domain I antibodies have been developed. First reports on domain I reactivity used a baculovirus system to express β 2 GPI that lacked one or more domains.…”