FRI0327 Reliability of la and diagnostic performance of aps/pt in different clinical settings of aps: a multicenter study. (12th June 2018)

• Record Type: Journal Article
• Authors: Radin, M.; Cecchi, I.; Rubini, E.; Scotta, A.M.; Rolla, R.; Montaruli, B.; Pergolini, P.; Mengozzi, G.; Muccini, E.; Roccatello, D.; Sciascia, S.
• Is Part Of: Annals of the rheumatic diseases. Volume 77(2018)Supplement 2
• Page Start: 700
• Page End: 700
• Publication Date: 2018-06-12
• Subjects: Rheumatism -- Periodicals; 616.723005
• DOI: 10.1136/annrheumdis-2018-eular.6206
• Languages: English
• ISSNs: 0003-4967

Abstract

Abstract : Background: Correct interpretation of lupus anticoagulant (LA) tests is crucial for diagnosis of antiphospholipid syndrome (APS). However, testing patients during vitamin K antagonist (VKA) or other anticoagulant remains a contentious issue and has been discouraged by official guidelines 1 because of interpretational problems affecting the mixing test. Similarly, the clinical significance of weak LA, especially in the context of VKA, remains uncertain and certainly needs a more thorough evaluation. Autoantibodies that recognise a phosphatidylserine/prothrombin (PS/PT) complex have been reported to be associated with APSandmay have diagnostic relevance in these settings. Objectives: To evaluate the reproducibility of LA testing when performed in different centres and to assess the diagnostic performance of anti-PS/PT in different clinical settings of APS. Methods: aPL testing was performed in a blind fashion in 4 centres. LA was tested as per the current criteria from the ISTH Subcommittee on LA-Phospholipid-dependent antibodies. 1 Thirty-two patients were enrolled in this study, as follows: 13 patients with thrombotic APS treated with vitamin K antagonist; 5 patients thrombotic APS treated with DOAC; 14 patients with transitory/low aPL titer. Anti-PS/PT IgG/IgM (aPS/PT, Inova Diagnostics)were tested by ELISA. We analysed the categorical agreement and degree of linear association, for LA and aPS/PT, respectively. Results: Demographic, clinical and laboratory characteristics are summarised in table 1. Categorical agreement for LA among the centres, as expressed by Cohen's kappa coefficients, ranged between 0.61 and 0.80 (as substantial agreement). The correlation among quantitative results in the aPS/PT IgG was strong (when dichotomizing for positive Vs. negative results, Cohen's kappa coefficients=0.81–1. Spearman rho 0.84). We observed 12 (37.5% of the total) cases (7/12, 58%patients on VKA) in which LA results were discordant(as defined by lack of agreement in ≥2 laboratories) or inconclusive. Conversely, in those cases, we observed a good correlation for aPS/PT IgG testing (Cohen's kappa coefficients=0.81–1, Spearman rho 0.86). Conclusions: Despite the progress in the standardisation of aPL testing, we observed up to 37.5% of discrepant results for LA, especially in patients on VKA. Our findings showed that some discordances in the reliability of LA testing still exist. The introduction of aPS/PT antibodies in the diagnostic process of APS might represent a further diagnostic tool, especially when LA is not available or nor reliable. Reference: [1] Pengo V, et al. Update of the guidelines for lupus anticoagulant detection. Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis. J Thromb Haemost2009;7:1737–40. Disclosure of Interest: None declared