Thromboelastometry Shows a Prothrombotic State in Systemic Lupus Erythematosus Related to Diminished Fibrinolysis and Microparticle-Derived Tissue Factor

Background: Systemic Lupus Erythematosus (SLE) is an autoimmune disorder of unknown origin with a high mortality pattern due to the development of a premature cardiovascular disease. The presence in these patients of a dysfunctional endothelium together with a hypercoagulable milieu may contribute to an increased incidence of thrombotic events. Increased thrombin generation, elevated levels of circulating microparticles and plasmatic levels of PAI-1 may contribute to the prothrombotic phenotype of the disease but data are scarce.

Objectives: 1- To characterize the prothrombotic state in SLE by rotational thromboelastometry (ROTEM) and thrombin generation linked to tissue factor bearing microparticles. 2- To evaluate endothelial damage in patients with SLE and its relationship with the prothrombotic state of the disease. 3- To evaluate the influence of PAI-1 in the prothrombotic state of SLE.

Material and methods: 39 patients with SLE and 25 sex and age matched healthy subjects were included. Whole blood was drawn in standard BD sodium citrate tubes (3.2%). ROTEM was performed in naTEM condition. Clotting time (CT, time from start of measurement until initiation of clotting [in seconds], alpha angle, which reflects the rate of fibrin polymerisation (tangent to the curve at 2-mm amplitude [in degrees]), maximum clot firmness, which reflects the maximum tensile strength of the thrombus (MCF, [in mm]), the time that clot takes to increase from 2mm above baseline to 20mm above baseline (CFT) and A5, amplitude at 5 min, were recorded.

To evaluate the presence of tissue factor bearing microparticles, thrombin generation was determined by Calibrated Automated Thrombogram (CAT) in presence of 4 mM phospholipid (MP-Reagent, Diagnostica Stago, Spain). The endogenous thrombin potential (ETP, the total amount of thrombin generated over time); the lag time (the time to the beginning of the explosive burst of thrombin generation); the peak height of the curve (the maximum thrombin concentration produced); and the time to the peak were evaluated.

Antigenic levels of E-selectin and PAI-1 were determined by ELISA (R&D Systems,MN, USA and Affymetrix eBioscience, Vienna, Austria) respectively.

Results: ROTEM parameters showed a hypercoagulable profile in LES patients. CT and CFT were shorter (p<0.001 in both cases), and MCF, alpha angle and A5 were higher (p<0.001, p<0.02 and p<0.001 respectively) when compared to healthy controls. On the other hand, CAT  parameters did not show differences between both groups. Nevertheless, in LES patients but not in controls, CAT parameters significantly correlated with ROTEM ones (Table 1).

		CT	CFT	MCF	MCF-t	alpha	A5	A10
ETP(MP)	r	-,301	-,375*	,369*	-,368*	,378*	,364*	,393*
	p	,084	0,028*	0,031*	0,032*	0,027*	0,034*	0,021*
	N	34	34	34	34	34	34	34
Peak(MP)	r	-,353*	-,396*	,372*	-,345*	,396*	,393*	,402*
	p	0,040*	0,020*	0,030*	0,045*	0,020*	0,021*	0,018*
	N	34	34	34	34	34	34	34
ttPeak(MP)	r	,240	,222	-,242	,217	-,223	-,209	-,210
	p	,171	,207	,168	,217	,205	,236	,232
	N	34	34	34	34	34	34	34

Table 1- Correlations in the LES patients group between CAT and ROTEM parameters. Analyses were performed with Spearman test. N: number of determinations; p* denotes significance.

In order to evaluate endothelial damage, plasma E-selectin and PAI-1 were determined. No differences were found in E-selectin level whereas increased PAI-1 levels were seen in LES group (p<0.006). PAI-1 did not correlate to ROTEM parameters.

Conclusions: ROTEM can detect a hypercoagulable state in patients with SLE. The hypercoagulable state may be linked to increased tissue factor bearing microparticles and increased PAI-1 plasma levels.