Antibodies to
prothrombin in solid phase (
aPT) and those to phosphatidiyserine-
prothrombin complex (aPS/PT) have been suggested to strongly correlate with the presence of
lupus anticoagulant (LA). As their clinical diagnostic value and true relationship with the LA remains elusive, we designed this study to evaluate the prevalence and significance of
aPT and aPS/PT in a large cohort of patients with and without LA. Samples from 257 patients were included.
aPT and aPS/PT were tested by ELISA. LA was tested as per the current criteria from the ISTH Subcommittee on LA-
Phospholipid-dependent
antibodies. aPS/PT and
aPT were found in 51% and 32% of LA-positive (LA+ve) patients and in 22% and 28% of LA-negative (LA-ve) patients, respectively.
Thrombosis, particularly
venous thrombosis was associated with
IgG aPT in the LA+ve group (p=0.0006) and in the LA-ve group (p=0.017).
Antibodies to
phosphatidylserine-
prothrombin, either
IgG and
IgM were associated with
thrombosis in general (p=0.0003) in particularly with
venous thrombosis in the LA+ve group (p<0.0001 for
IgG and p=0.025 for
IgM; respectively) and the LA-ve group (p=0.028, 0.02 and 0.001, respectively). Further multivariate logistic regression analysis showed that LA and of
IgG and/or
IgM aPS/PT were independent risk factors for
thrombosis and pregnancy loss. In conclusion, aPS/PT, but not
aPT, are more frequently found in patients with LA. Their association with
thrombosis seems to be independent of the presence of LA.