The clinical performance of a chemiluminescent immunoassay in detecting anti-cardiolipin and anti-β2 glycoprotein I antibodies. A comparison with a homemade ELISA method

BACKGROUND: Fully automated chemiluminescence immunoassays (CLIAs) are emerging technologies for the detection of anti-cardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) antibodies for anti-phospholipid syndrome (APS) classification, which is commonly based on an enzyme-linked immunosorbent assay (ELISA) test result. CLIA and a homemade ELISA were used in this study to detect these antibodies, and their performances were compared. METHODS: Sera were collected from 104 patients with primary APS, 88 seronegative subjects who met the clinical but not the laboratory criteria for APS, and 150 control subjects. IgG/IgM aCL and IgG/IgM anti-β2GPI antibodies were determined in the sera using a CLIA (HemosIL AcuStar®) and a homemade ELISA. RESULTS: CLIA had a significantly lower comparative sensitivity for IgM aCL and IgG/IgM IgG anti-β2GPI antibodies; its comparative specificity was higher with respect to ELISA for IgM aCL and IgM anti-β2GPI antibodies. The two techniques showed a high, significant agreement (p<0.001) and a significant titer correlation (p<0.001). CLIA also detected IgG/IgM aCL and IgG anti-β2GPI antibodies in the seronegative patients. There was a significantly higher prevalence of IgG aCL and IgG anti-β2GPI antibodies (p<0.001 and p=0.01, respectively) in those patients with respect to that in the control population. CONCLUSIONS: Despite a lower comparative sensitivity, CLIA showed a higher comparative specificity for some aPL and a good level of agreement and correlation with a homemade ELISA. CLIA also detected some aCL and anti-β2GPI antibodies in the seronegative patients not usually identified by homemade ELISA.