Evaluation of phosphatidylserine-dependent antiprothrombin antibody testing for the diagnosis of antiphospholipid syndrome: results of an international multicentre study

Abstract

Objective: A task force of scientists at the International Congress on Antiphospholipid Antibodies recognized that phosphatidylserine-dependent antiprothrombin antibodies (aPS/ PT) might contribute to a better identification of antiphospholipid syndrome (APS). Accordingly, initial and replication retrospective, cross-sectional multicentre studies were conducted to ascertain the value of aPS/PT for APS diagnosis. Methods: In the initial study (eight centres, seven countries), clinical/laboratory data were retrospectively collected. Serum/plasma samples were tested for IgG aPS/PT at Inova Diagnostics (Inova) using two ELISA kits. A replication study (five centres, five countries) was carried out afterwards. Results: In the initial study (n ¼ 247), a moderate agreement between the IgG aPS/PT Inova and MBL ELISA kits was observed (k ¼ 0.598). IgG aPS/PT were more prevalent in APS patients (51%) than in those without (9%), OR 10.8, 95% CI (4.0-29.3), p < 0.0001. Sensitivity, specificity, positive (LRþ) and negative (LR-) likelihood ratio of IgG aPS/PT for APS diagnosis were 51%, 91%, 5.9 and 0.5, respectively. In the replication study (n ¼ 214), a moderate/substantial agreement between the IgG aPS/PT results obtained with both ELISA kits was observed (k ¼ 0.630). IgG aPS/PT were more prevalent in APS patients (47%) than in those without (12%), OR 6.4, 95% CI (2.6-16), p < 0.0001. Sensitivity, specificity, LR þ and LR-for APS diagnosis were 47%, 88%, 3.9 and 0.6, respectively. Conclusions: IgG aPS/PT detection is an easily performed laboratory parameter that might contribute to a better and more complete identification of patients with APS. Lupus (2016) 0, 1-11.

Exploring the plasmatic platelet-activating factor acetylhydrolase activity in patients with anti-phospholipid antibodies

“…We and others recently demonstrated an important role of aPS/PT antibodies in the serological diagnosis of APS [5, 26]; however, the therapeutic management of patients characterized by the presence of isolated aPS/PT remains an open issue. Patients with isolated aPS/PT antibodies disclosed lower, BDs-like, PAF-AH as compared to patients with positive aβ2GPI antibodies.…”

Closing the Serological Gap in the Antiphospholipid Syndrome: The Value of “Non-criteria” Antiphospholipid Antibodies

“…Assays for aPL antibodies are technically considerably more demanding to manufacture and control than many other conventional assays. In contrast to aPS/PT, which is commercially available and has been evaluated in a recent international multicenter study and subjected to rigorous FDA review, the other assays are less standardized and need additional studies, especially to validate their specificity using disease controls 28 . In our study, aCL/Vim antibodies were detected in 44.9% of the SP-APS patients and in 16.2% of the SN-APS patients, suggesting a potential utility.…”

The antiphospholipid syndrome – often overlooked cause of vascular occlusions?

“…Prothrombin is in similarity to b 2 GPI a phospholipid binding protein. Flecker et al described already in 1988 that antiprothrombin antibodies had lupus anticoagulant activity [107], and several studies thereafter have confirmed this observation [108,109] and also linked aPS/PT antibodies to clinical symptoms of APS [110,111]. Presently, there is an ongoing discussion on the clinical value of aPS/PT antibodies and if they should be included in APS criteria.…”