REPORT OF THE FIRST FRENCH ANTICARDIOLIPIN ANTIBODIES STANDARDIZATION WORKSHOP

Anticardiolipine antibodies are a marker of the antiphospholipid syndrome. They are detected by Elisa. Despite its simplicity, the results obtained by this assay are not always reproducible despite several worldwide standardizations and the distribution of calibration sera by EN Harris. On 4 Decembre 1992, the First French Anticardiolipin Antibodies Standardization Workshop was held in Paris. Eight coded standards weve sent to 33 laboratories in France, one in Switzerland and one in Luxembourg. Some of them used several assays. Agreement between qualitative results was goad for samples with high and moderate level of antibodies. But the results expressed in IgC antiphospholipid units were scattered, the interlaboratory coefficient of variation for each of the eight standards was higher than 70%, though the within-run coefficient of variation had a median value of 10%. Assays using bovine serum for the blocking buffer and for the dilution buffer seemed to give more reproducible results than assays using purified bovine serum albumin (p < 0.001). For only nine assays out of 38 which expressed results quantitatively, was a linear regression observed between the dilutions of a sample and the results expressed in IgG antiphospholipid units. Absence of linearity is an obstacle which must be overcome if we wish to compare quantitative results obtained by different laboratories.