Multicenter Evaluation of Nine Commercial Kits for the Quantitation of Anticardiolipin Antibodies

Abstract

SummaryThe performances of nine commercial kits and an in-house method (HM) for the quantitation of anticardiolipin antibodies (ACA) have been evaluated in a multicenter study. Ninety control and patient samples and six standards from Louisville University were run with kits and with the HM. Marked differences in positivity rate between kits were observed, ranging from 31 to 60% for IgG and 6 to 50% for IgM. Concordance between kits occurred in 59 and 51% of samples for IgG and IgM respectively. Concordance coefficients (kappa) ranged from 0.13 to 0.92. Slopes of regression lines between the declared units of Louisville standards and the units measured from the calibrators of the kits showed great diversity and ranged from 0.159 to 0.931 for IgG and from 0.236 to 0.836 for IgM. The β2-glycoprotein I (β2-GPI) content of the dilution buffers and the wells supplied with the kits revealed noticeable differences. However samples containing anti-(β2-GPI antibodies were classified similarly by all but one kit. In contrast the ability to measure samples devoid of anti-β2-GPI antibodies differed markedly between the kits.This study shows that differences in positivity rates between the commercial kits may contribute to the differences in ACA prevalence rate found in the literature. The choice of cut-off levels may partly explain the moderate concordance between the kits. In addition some samples behave very differently depending on the kits. In spite of the expression of results in PL units, standardization of ACA assays has not been achieved.

Antiphospholipid/antiprotein antibodies, hemostasis-related autoantibodies, and plasma homocysteine as risk factors for a first early pregnancy loss: a matched case-control study

“…Plasma anticardiolipin immunoglobulin G (IgG) and IgM antibodies were measured according to an adaptation of the in-house method that has been previously published by Reber et al 24 In brief, plates (Immunoplate Maxisorp; Nunc, Roskilde, Denmark) were coated with cardiolipin (50 g/mL in methanol; Sigma, St Louis, MO) or just with methanol (nonspecific binding wells) and incubated overnight at 4°C. Blocking and dilution solutions were phosphate-buffered saline (PBS) with 10% fetal calf serum.…”

Comparative incidence of a first thrombotic event in purely obstetric antiphospholipid syndrome with pregnancy loss: the NOH-APS observational study

“…8,9 All coagulation assays were performed on the STA-R automatic coagulation analyzer (Stago). Plasma aCL IgG and IgM Abs were measured according to an adaptation of the in-house ELISA method that has been described previously by Reber et al 10 Plasma a␤2GP1 IgG and IgM Abs were measured according to an ELISA developed in-house using ␤2-glycoprotein I isolated from freshly frozen human citrated plasma as described by Horbach et al 11 LA activities were quantified using the results of the mixing test and are expressed as the ratio of the aPTT test result from the patient and healthy pooled plasma mixed 1:1, divided by the aPTT test result from the healthy pooled plasma (normal value Ͻ 1.22). All plasmas were secondarily quantified for the 4 solid-phase aPLAbs based on calibration curves performed using the Sapporo standards HCAL and EY2C9 kindly provided by The Binding Site staff (Saint Egrève, France).…”

Aspirin inhibits endothelial cell activation induced by antiphospholipid antibodies

“…The titers of anticardiolipin IgG were determined as previously described [21]. Plasma levels of antib 2 GP1 IgG and IgM were evaluated by ELISA [22].…”