A STANDARD ANTI-CARDIOLIPIN (aCL) TEST: USEFULNESS IN IDENTIFICATION OF THE ANTI-PHOSPHOLIPID SYNDROME

Abstract

Some, but not all, patients with the lupus anticoagulant and anti-cardiolipin antibodies are prone to thrombosis, fetal loss and thrombocytopenia. It will be important to identify the particular sub-group of patients with anti-phospholipid (aPL) antibodies most subject to these clinical disorders. A preliminary study has shown that the level of IgG aCL antibody is predicitive for thrombosis, fetal loss, and thrombocytopenia but it will be difficult to substantiate (or refute) these findings unless there is a uniform system to measure aCL antibody levels.Five test sera with defined IgG and IgM aCL levels are currently available to laboratories wishing to standardise the aCL test. The concentrations of aCL in these sera cover the full sensitive range of aCL solid phase assays. Using these. 5 test sera to calibrate our assay system, sera from 3000 patients were analysed: 1400 healthy adults and 1600 consecutive patients with autoimmune disorders. All sera from healthy adults had aCL levels below 10GPL (IgG aCL) or below 10MPL (IgM aCL) units. Of the 1600 autoimmune patients, 115 had levels above 5 GPL and/ or 5MPL units. More than 2/3 of patients with IgG aCL levels above 20 GPL units (30 patients) had thrombosis or fetal loss, but the frequency of these disorders decreased in the 10-20 GPL and 5-10 GPL unit groups. Of the 9 patients with IgM aCL levels above 15 MPL units, 6 had thrombosis or fetal loss.The availability of reference sera to measure IgG and IgM aCL antibody levels may better enable multicenter studies to be performed. A relatively uniform system of measurement may also enable easier identification and management of patients with the anti-phospholipid syndrome.