Automated Chemiluminescence Assay Identifies Antiphospholipid Antibodies

The laboratory diagnosis of antiphospholipid antibody syndrome (APS) requires the demonstration of antiphospholipid antibodies (aPL) by lupus anticoagulant (LAC) measured through coagulation assays.

A new chemiluminescence automated system has been proposed that can improve the reproducibility and reduce interlaboratory variation as the laboratory diagnosis of the APS remains a challenge for each laboratory worker in the field.

Scientists at the Sapienza University (Rome, Italy) analyzed blood samples from 314 consecutive individuals. There were 63 with clinical APS; 73 patients did not show clinical manifestations of APS, but were positive for anticardiolipin antibodies (aCL); 15 patients who were LAC positive, and had shown venous and/or arterial thrombosis; and 163 subjects were healthy blood donors and showed no signs or symptoms of APS.

Serum samples were tested with commercial autoantibody assays and lupus anticoagulant assays. Anticardiolipin antibodies, immunoglobulin G (IgG) and IgM were tested by chemiluminescence assay on the Zenit RA immunoanalyzer (A. Menarini Diagnostics, Florence, Italy). Zenit RA, a random-access immunoanalyzer, uses a two-step immunoassay method based on the principle of chemiluminescence.

The results of the study showed while almost all the sera from APS patients who were positive for IgG aCL and anti-β2- glycoprotein I (GPI) by enzyme linked immunosorbent assay (ELISA), were also positive for IgG aCl by chemiluminescence. Only 30.13% of patients without clinical manifestations of APS confirmed the positive test by chemiluminescence, although were positive for aCL and persistently negative for anti-β2-GPI IgG by ELISA and LAC. Both ELISA tests were products of INOVA Diagnostic Inc. (San Diego, CA, USA).

The highest positivity of aCL by chemiluminescence was detected among patients with rheumatic disorders (50%), followed by patients with neurological disorders (33.3%) or infectious diseases (25%).This group of patients without clinical manifestations of APS, were positive for aCL by ELISA and persistently negative for anti-β2-GPI by ELISA and LAC. The authors concluded that the results suggest that the new technology of automated chemiluminescence assay for measuring aPL may represent a useful tool to identify “true” APS patients. The study was published in the May 2012 issue of the Journal of Immunological Methods.

Related Links:
Sapienza University
A. Menarini Diagnostics
INOVA Diagnostic