Summary
We have compared the prevalence of antiphospholipid antibodies (APA) measured by enzyme-linked
immunosorbent assay (ELISA), in 119 selected patients using five different antigens:
bovine cardiolipin, phosphatidylserine, phosphatidylinositol, bovine partial thromboplastin
and human brain partial thromboplastin. All the plasmas have been evaluated for the
presence of lupus anticoagulant (LA) activity by clotting techniques. We found a significant
association between the incidence of LA and APA (p <0.001), only moderate agreement
between the prolongation of the activated partial thromboplastin time (APTT) and ELISAs
(r around 0.50) and a good agreement between the ELISAs (r around 0.80). The combination
of antibodies against cardiolipin (ACA) and human brain partial thromboplastin (AHPTA)
allowed the detection of antibodies in most of the LA positive cases. ACA, AHPTA and
antiphosphatidylinositol antibodies detected all the positive samples. Six patients
(5%) had a single APA detected. The clinical associations of APA according to phospholipid
specificity, immunoglobulin isotype and titer are shown.