Composite Risk Score With PC4d, C3, and LAC Linked to Thrombosis in SLE

A composite thrombosis risk equation including platelet C4d, low C3, and lupus anticoagulant is strongly associated with thrombosis in systemic lupus erythematosus.

In patients with systemic lupus erythematosus (SLE), a composite risk score that includes C4d products deposited on platelets (PC4d), low C3 levels, and low lupus anticoagulant (LAC) levels is associated with recent thrombosis, thus recognizing the multifactorial nature of thrombosis in SLE, according to a study published in the journal Lupus Science & Medicine.

In this cross-sectional analysis, investigators sought to assess the link between complement abnormalities and a history of thrombosis among patients with SLE, all of whom were enrolled at a single lupus center in the Baltimore, Maryland, area. A total of 149 consented patients with SLE participated in the study, 16 of whom had been classified with thrombotic events and 133 of whom had been classified without thrombotic events in the past 5 years. The mean participant age was 48.3 ± 1.2 years; 85.9% of the patients were women.

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Abnormal PC4d (≥20 units) was calculated with the use of flow cytometry. C3 and LAC levels were measured with the use of immunoturbidimetry and dilute Russell’s viper venom time (>37 seconds), respectively. Antiphosphatidyl serine/prothrombin (PS/PT) antibody status (immunoglobulin G), which was evaluated as an alternative to LAC, was calculated via the use of immunoassays.

Abnormal PC4d (odds ratio [OR], 8.4; 95% CI, 2.8-24.8), low C3 level (OR, 9.5; 95% CI, 3.0-30.30), low LAC level (OR, 5.4; 95% CI, 1.3-22.3), and low anti-PS/PT immunoglobulin G status (OR, 3.4; 95% CI, 1.2-9.7) were all significantly associated with thrombosis (P <.05).

Cumulatively, the presence of PC4d, low C3, and LAC abnormalities as a composite risk score was significantly higher in the presence of thrombosis (1.93 ±0.25) than in the absence of thrombosis (0.81 ± 0.06; P <.01). In each of the units in this composite risk score, an OR of 5.2 was reported (95% CI, 2.5-10.7), which was significantly associated with the presence of thrombosis (P <.01). The composite risk score that used anti-PS/PT score instead of LAC level was also significantly associated with thrombosis (P <.01).

The investigators concluded that based on the findings from this study, in patients with SLE, the composite score of risk factors outperformed the use of single risk factors alone with respect to the association of disease with thrombosis.


Petri MA, Conklin J, O’Malley T, Dervieux T. Platelet-bound C4d, low C3 and lupus anticoagulant associate with thrombosis in SLE. Lupus Sci Med. 2019;6:e000318.