The Utility of Thromboelastography (TEG) In the Management of Patients with Isolated Antiphospholipid Antibodies (aPL) or Primary Antiphospholipid Syndrome (PAPS)

Antiphospholipid syndrome (APS) is an immune disorder characterised by recurrent thrombosis and/or complications during pregnancy associated with the presence of persistent antiphospholipid antibodies (aPL). Several mechanisms have been proposed to underlie the pathogenic mechanisms of aPL but studies of markers of coagulation activity and thrombin generation suggest healthy individuals with aPL do not usually have a hypercoagulable state.

Thromboelastography (TEG) is a global measure of haemostasis and has been shown to demonstrate hypercoagulable states. Also, studies have shown women with recurrent first trimester loss have hyercoagulable TEG parameters. There have been no studies to date assessing the use of TEG in patients with aPL/PAPS.

The aim of this study was to assess the potential role of TEG to assess hypercoagulability of individuals with antiphospholipid antibodies or PAPS.

Local ethical committee approval was obtained. Samples were obtained from patients attending clinics at our institution who had PAPS according to International Consensus statement criteria, or had persistent aPL without associated complications. The control group were recruited from hospital staff who were not known to have aPL, were non smokers and not taking the oral contraceptive pill.

Control blood samples were obtained from 17 healthy non-pregnant women (median age 37.5 (range 20–58) years). Patient blood samples were obtained from 39 women with apL and previous thrombosis, 5 of whom had previous pregnancy morbidity, 3 of whom were smokers and all of whom were on oral vitamin K antagonists (median 47 (23-61)), 14 women with obstetric APS and no history of thrombosis, 2 of whom were smokers (median 41 (32-54)), and 17 women with isolated aPL, 2 of whom were smokers (median 43.5 (19-73)).

Fresh whole blood was drawn by flawless venepuncture into tubes containing citrate 0.105M and stored at room temperature for 30 minutes prior to analysis. 500μl of whole blood was activated with 12.5μl of Kaolin and thromboelastography was performed by the same technician on 340μl of activated blood using a TEG® analyzer according to the manufacturer's protocol. Statistical analysis of all TEG parameters was performed using the unpaired t-test. A P-value of <0.05 was considered statistically significant.

Results of TEG parameters including R time, K, α angle, Maximal amplitude (MA), Coagulation Index (CI), and % lysis after 30 minutes (LY30) are shown below in table described as means and standard deviations.

A significantly prolonged R time was found in the thrombotic APS group compared to aPL group (p<0.01) and control group (p<0.01), reflecting the use of oral vitamin K antagonists in this group. There was no significant difference in any other parameters except for LY30.

LY30 was significantly greater in patients with thrombotic APS compared to the aPL group (p=0.03) and in patients with) obstetric APS (p=0.02) and isolated aPL (p<0.01) compared to controls.

Healthy individuals with aPL or PAPS do not appear to have a hypercoagulable state by TEG criteria. Indeed, there is evidence of significantly increased fibrinolytic activity compared to controls. This is currently unexplained and worthy of further study.

Breen:NovoNordisk: Research Funding.