Anti‐phosphatidylserine prothrombin antibodies as a predictor of the lupus anticoagulant in an all‐comer population

Abstract

Background: Anti-phosphatidylserine prothrombin antibodies (aPSPT) are reported to be highly associated with the lupus anticoagulant (LAC) in established antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) cohorts. Further, aPSPT has been suggested to be a useful surrogate LAC marker. However, validation studies replicating this relationship in an all-comer study population in the diagnostic clinical setting are lacking.Objectives: To determine the sensitivity and specificity of aPSPT to the LAC in an allcomer population undergoing evaluation for suspected APS.Methods: An assembled cross-sectional cohort from June 2017 to December 2018 undergoing APS evaluations across all medical specialties were reviewed for LAC, aPSPT, anti-cardiolipin (aCL), and anti-β2 glycoprotein-1 (β2GP1). Sensitivities, specificities, and negative and positive predictive values were calculated. Results and Conclusions:A cohort of 166 eligible patients was identified. Seventyone percent were female, 89% White, 15% with SLE, and 21% with APS. The aPSPT was found to be the most specific to the LAC. Specificity of IgG aPSPT was 100% (96%-100%) and IgM aPSPT was 97% (91%-100%) to the LAC. Corresponding positive predictive value for IgG aPSPT was 100% (89%-100%) and IgM aPSPT was 95% (84%-99%). In contrast, the sensitivities of aPSPT to the LAC were less robust, only in the 40%-50% range. The findings validate previously reported findings and lends extension to an all-comer population. These findings corroborate aPSPT as a potentially useful clinical marker of the LAC.

Frequency and Clinical Significance Anti-PS/PT Antibodies in Patients with Antiphospholipid Syndrome—Single Centre Observational Study in the United Kingdom

“…The strong correlation between the presence of LA and the presence of anti-PS/PT has been noted in previous studies 14,15 including a multicenter study conducted by Sciascia et al 16,17 This has a major clinical significance, as anti-PS/PT can be used in situations where detection of LA is problematic: the most significant being patients on anti-coagulation therapy (DOACs and warfarin), which can lead to false positive LA results. 6 Currently, either LA testing is postponed until anticoagulation is completed, the patient is switched to alternative anticoagulant such as low molecular weight heparin or alternative tests such as Taipan venom test/Ecarin clotting time are employed.…”

Evolution of Antiphospholipid Syndrome

“…73 Also associated with clinical features of APS, anti-PS/PT are increasingly recognized as a key aPL population responsible for LA positivity. [74][75][76][77] The strong correlation between LA and anti-PS/PT has been extensively noted [78][79][80] including in a multicenter study conducted by Sciascia et al 81 This observation has major clinical significance, as anti-PS/PT can be used in situations where detection of LA is problematic, the most significant being patients on anticoagulation therapy, which can lead to false-positive LA results. 82…”

Noncriteria antiphospholipid antibodies in antiphospholipid syndrome

“…This means that LA cannot be replaced by aPS/PT one-on-one. 61,64,70 Currently, aPS/PT testing's superior value in the diagnostic workup of thrombotic and obstetric APS is limited. However, aPS/PT can be useful in specific subsets of patients with obstetric complications.…”

“…Although a large overlap exists, the meta‐analysis and additional papers have shown an incomplete overlap with LA. This means that LA cannot be replaced by aPS/PT one‐on‐one 61,64,70 …”