Abstract
IntroductionDiagnosis of antiphospholipid syndrome (APS) still remains a laboratory challenge due to the great diversity of antiphospholipid antibodies (aPL) and their significance regarding APS-diagnostic criteria.MethodsA multi-line dot assay (MLDA) employing phosphatidylserine (PS), phosphatidylinositol (PI), cardiolipin (CL), and beta2-glycoprotein I (β2 GPI) was used to detect aPL, immunoglobulin G (IgG) and immunoglobulin M (IgM) in 85 APS patients, 65 disease controls, and 79 blood donors. For comparison, anti-CL and anti-β2 GPI IgG and IgM were detected by enzyme-linked immunosorbent assay (ELISA).ResultsThe level of agreement of both methods was good for anti-CL IgG, moderate for anti-CL IgM, very good for anti-β2 GPI IgG, and moderate for anti-β2 GPI IgM (kappa = 0.641, 0.507, 0.803 and 0.506, respectively). The frequency of observed discrepancies for anti-CL IgG (1.75%), anti-CL IgM (3.93%), anti-β2 GPI IgG (1.75%), and anti-β2 GPI IgM (0.87%) was low (McNemar test, P < 0.05, not-significant, respectively). Sensitivity, specificity, positive (+LR) and negative (-LR) likelihood ratios for at least one positive aPL antibody assessed by ELISA were 58.8%, 95.8%, 14.1, and 0.4, respectively, and for at least three positive aPl IgM and/or one positive aPL IgG by MLDA were 67.1%, 96.5%, 19.3, and 0.3, respectively. The frequency of IgM to PI, PS and CL, and combination of three or more aPL IgM detected by MLDA was significantly higher in APS patients with cerebral transient ischemia (P < 0.05, respectively).ConclusionsThe novel MLDA is a readily available, single-step, sensitive diagnostic tool for the multiplex detection of aPL antibodies in APS and a potential alternative for single aPL antibody testing by ELISA.
Highlights
Diagnosis of antiphospholipid syndrome (APS) still remains a laboratory challenge due to the great diversity of antiphospholipid antibodies and their significance regarding APS-diagnostic criteria
For comparison of enzyme-linked immunosorbent assay (ELISA) and multi-line dot assay (MLDA) techniques, the human monoclonal antibody (mAb) immunoglobulin G (IgG) HL7G and HL5B, and the human immunoglobulin M (IgM) EY2C9 were run in anti-CL and anti-b2 beta2-glycoprotein I (GPI) ELISAs and in the novel MLDA
The level of antiphospholipid antibodies (aPL) specific IgM required to reach the cut-offs in the respective ELISAs were similar to the concentration of specific IgM revealing a cut-off band in MLDA
Summary
Diagnosis of antiphospholipid syndrome (APS) still remains a laboratory challenge due to the great diversity of antiphospholipid antibodies (aPL) and their significance regarding APS-diagnostic criteria. According to a recently updated international consensus statement, the association of at least diagnosis of APS. APL antibodies recognizing cofactor proteins in complex with phospholipids have been reported to have a closer association with clinical manifestations in APS [8,9,10,11,12,13]. Despite the revised APS consensus criteria, diagnosis of APS remains challenging [14]. According to the updated consensus statement, anti-b2 GPI and anti-CL IgG and IgM antibodies and LAC are recommended for aPL antibody testing [5]. With regard to the detection techniques applied, antiphospholipid antibodies have been mainly detected by solid-phase ELISA so far
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