Multiple antiphospholipid tests do not increase the diagnostic yield in antiphospholipid syndrome

The family of antiphospholipid antibodies (aPL) includes a heterogeneous po pulation of autoantibodies whose specificity is directed against not only p hospholipids, but their complex with plasma proteins. Anticardiolipin antib odies (aCL) and lupus anticoagulant (LA) tests are widely performed to scre en the aPL family which is associated with thrombotic complications in pati ents with systemic lupus erythematosus (SLE) or antiphospholipid syndrome ( APS). The clinical significance of other aPL tests, including antibodies ag ainst phosphatidylserine (aPS), phosphatidylinositol (aPI), phosphatidic ac id (aPA), phosphatidyl choline (aPC) and phosphatidylethanolamine (aPE), ha s not been established. The purpose of this study was to evaluate whether m ultiple aPL tests have enhanced diagnostic value for APS. We tested IgG/M/A aPS, aPI, aPA, aPC and aPE by ELISA using 10% bovine serum as blocking and sample diluent in 26 SLE patients with clinical manifestations of APS, but negative for both aCL and LA (Group 1). The results were compared with 32 SLE patients without any features of APS (Group 2) and 24 SLE patients with APS (aCL and/or LA positive) (Group 3). In Group 1, 1/26 (4%) was positive for IgA aPE, less frequent than in other groups, and none of the patients had any other aPL. In Group 2, 1/32 (3%) was positive for aPS, two (6%) for aPI, one (3%) for aPA and four (12.5%) for aPE. None was positive for aPC. In the third group, 13/24 (54%) were positive for aPS, 11 (46%) for aPI, 1 5 (63%) for aPA, four (17%) for aPC and seven (29%) for aPE. Since aPE was found in some patients, we extended the study, including 207 SLE patients, and tested aPE. IgG/M/A aPE was found in six (3%), 10 (5%) and 21 (10%), re spectively, but no association was found between aPE and any clinical featu res of APS. This study suggests that screening by multiple aPL tests does n ot increase the diagnostic yield in APS.