Anticardiolipin antibodies and thrombosis: buffer's influence on the detection and quantitation of anticardiolipin antibody measured by ELISA.
The influence of adult bovine serum (ABS) and fetal calf serum (FCS) on IgG anticardiolipin antibodies (ACA) levels measured by ELISA has been investigated. In control subjects the frequency of the optical density (O.D.) distribution was found to be non-gaussian. The O.D. of the 97th percentile was similar with both buffers, although the distribution of O.D. was statistically different (P less than 0.004). The slope of the dilution curves of two house standards as well as the curves obtained with reference standards were found to be very different depending on the buffer. In 55 consecutive patients with thrombotic events, recurrent fetal loss or auto-immune disorders, ACA positivity was also dependent on the way to express the data and the choice of the buffer: when O.D. values were read with their respective standard curves, IgG ACA positivity was 98% with FCS and 20% with ABS (P less than 0.001), but when the 97th percentile O.D. was considered, 40% were positive with FCS and 51% with ABS (n.s.). Furthermore 10 patients were found to be negative with FCS and positive with ABS and 4 others showed the inverse picture. Levels of positivity were also dependent on the buffer. These differences arise from the solution used to dilute the sera and not of that to block the plates. These methodological problems may explain some conflicting data found in the literature about the prevalence of ACA positivity.
Reber
G
G
Department of Medicine, University Cantonal Hospital, Geneva, Switzerland.
Tremblet
C
C
Bernard
C
C
Mermillod
B
B
de Moerloose
P
P
D000906:Antibodies / Q000032:analysis* / Q000592:standards; D002021:Buffers; D002308:Cardiolipins / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis / Q000592:standards; D013927:Thrombosis / Q000276:immunology*
D000906:Antibodies; D002021:Buffers; D002308:Cardiolipins; D007074:Immunoglobulin G