D-dimer level and the risk for thrombosis in systemic lupus erythematosus

Abstract

Background and objectives: Patients who have systemic lupus erythematosus (SLE) and manifest antiphospholipid antibodies (APA) are at increased risk for thrombosis; however, it is difficult to predict who will clot. This study tested the hypothesis that peak D-dimer level measured routinely during follow-up identifies whether a hypercoagulable state is developing and, therefore, the patient is at increased risk for thrombosis.

Design, setting, participants, & measurements: One hundred consecutive patients who had SLE with recurrent activity (71% renal SLE) and were evaluated for or enrolled in the Ohio SLE Study were studied. D-dimer testing was done annually and usually at SLE flare or other serious illness. When D-dimer was elevated, evaluation for thrombosis (large vessel, small vessel, or Libman-Sacks) was undertaken. Mean follow-up was 37.5 +/- 15 SD months.

Results: Of those with peak D-dimer <0.5 microg/ml (n = 46), 0% thrombosed, 33% had APA. Of those with peak D-dimer 0.5 to 2.0 microg/ml (n = 19), 6% thrombosed, 44% had APA. Of those with peak D-dimer >2.0 microg/ml (n = 36), 42% thrombosed, 76% had APA. The most common causes of elevated D-dimer in the absence of demonstrable thrombosis were SLE flare and systemic infection. D-dimer levels were usually elevated for several months before thrombosis.

Conclusions: Patients with SLE and normal D-dimer levels are at low risk for thrombosis, irrespective of APA status. Those with persistent unexplained elevated D-dimer levels, particularly when >2.0 microg/ml, are at high risk for thrombosis.

Figure 1.

Sequential changes in D-dimer levels before the diagnosis of the clotting event in the 15 patients who experienced clotting during study follow-up. Each patient is represented by a different symbol, which also has the assigned number that corresponds to the patients described in Table 3.

Figure 2.

Sequential changes in D-dimer levels in the 19 patients who had D-dimer levels >2.0 μg/ml and did not experience clotting either before or during study follow-up. All D-dimer measurements during study follow-up are shown. Each patient is indicated by a different symbol.