Reevaluation of predictive value of ACL and anti-β2GP1 antibody for thrombosis in patients with systemic lupus erythematosus: from a perspective of a practical world.

Detection of ACL (anticardiolipin, ACL) and anti-β2GP1 (beta2 glycoprotein1, β2GP1) antibody has been widely used, and the criteria of APS (Antiphospholipid syndrome, APS) have been used for the prediction of thrombosis in patients with SLE. What is the exact predictive value of these two antibodies? Is it really necessary to apply the criteria of APS to each patient just for the purpose of prediction of thrombosis? The aim of this retrospective study is to reevaluate the predictive value of different combination of ACL and anti-β2GP1 antibody for thrombosis formation in Chinese patients with SLE. Patients fulfilling the 1997 ACR classification criteria for SLE were enrolled and retrospectively analyzed. Thrombosis was confirmed by ultrasound, cerebral MRI, computed tomography pulmonary angiogram and angiography. Both IgG and IgM isotype of ACL and anti-β2GP1 antibody were detected with ELISA kit. ROC curves and other parameters of diagnostic test for different combination of ACL and anti-β2GP1 were analyzed and compared. 175 patients were recruited and thrombosis was diagnosed in 49 patients. In patients with thrombosis, 95.9% had been treated with glucocorticoids before detection of the two antibodies, 44.9% had hypertension and 53.1% had hyperlipidemia. ACL was positive in 28 patients (16%), and anti-β2GP1 antibody was positive in 21 patients (12%). The presence of a low or higher titer of either ACL (>12 RU/ml) or anti-β2GP1 antibody (>20 RU/ml) once has the highest predictive accuracy. The sensitivity, the specificity, the Youden's index and the area under ROC curve are 61.11%, 81.11%, 0.4222 and 0.711 respectively. A transient low or higher titer of ACL or anti-β2GP1 antibody had a good predictive value for thrombosis in patients with SLE, especially in those with other traditional risk factors for thrombosis and those treated with glucocorticoids.