The Relationship between D-dimer Combined with Red Blood Cell Distribution Width and the Activity of Systemic Lupus Erythematosus Disease

Background: Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disorder characterized by a wide range of clinical presentations and abnormal laboratory findings related to its diagnosis and activity state. Researchers have investigated many markers for their accuracy to reflect the activity status. Red blood cell distribution (RDW) and D dimer are easy obtainable markers that are related to inflammatory condition in many diseases. Combining more than one marker may be more beneficial in detecting and monitoring activity. Objective: This study aimed to investigate the relationship between D-dimer combined with RDW and SLE activity. Methods: A control group of twenty-five healthy persons, 25 active SLE patients and 25 inactive SLE patients participated in this cross-sectional investigation. Utilizing the SLE disease activity index-2000 (SLEDAI-2K), disease activity was evaluated. D-dimer and RDW were measured in all participants, while complement levels (C3, C4), antinuclear antibodies, anti-double stranded DNA, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were used to indicate activity status. Results: In the active SLE group, the mean RDW percentage was significantly higher (p < 0.001) than in the inactive and control groups. The D-dimer levels were significantly higher (p < 0.001) in the active SLE group than in the inactive and control groups. The SLEDAI score significantly correlated with RDW and D-dimer (r = 0.999, p > 0.001 and r = 0.671, p > 0.001, respectively). ROC curve analysis showed that D-dimer and RDW had AUC values of 0.961 and 0.945 respectively. On the other hand, the biggest AUC of RDW D-dimer combination (0.986) indicates stronger diagnostic effectiveness. Conclusions: Both RDW and D-dimer are useful indicators of SLE activity, and when combined, they are even more useful for determining the activity state in SLE patients.