Red blood cell distribution width-to-platelet ratio as a disease activity-associated factor in systemic lupus erythematosus

Abstract

Background: Although different clinical and experimental parameters have been used to estimate disease activity in systemic lupus erythematosus (SLE) patients, the relationship between red blood cell distribution width-to-platelet ratio (RPR) and disease activity in SLE has not been previously illuminated. Therefore, the aim of this study was to investigate the association between RPR levels and disease activity in SLE.

Methods: This study enrolled 105 SLE patients and 105 healthy subjects. We divided the patients into 2 groups using the SLE Disease Activity Index (SLEDAI) 2000. Group 1 included patients with SLEDAI score ≤9 (mild disease activity group) and group 2 with SLEDAI >9 (severe disease activity group). Correlations between RPR and disease activity were then analyzed. A subgroup follow-up analysis of 93 patients was conducted to explore the effect of SLE-related glucocorticoid therapy.

Results: The PLR and RPR values of SLE patients were significantly higher compared with the controls (both P < .001), whereas mean platelet volume was decreased (P < .05). The RPR level was found to be positively correlated with SLEDAI (r = 0.368, P < .001) and erythrocyte sedimentation rate (r = 0.313, P = .027). According to the receiver-operating characteristic (ROC) curve, the optimal cut-off value for predicting SLE using RPR was 0.073, and the area under ROC curve was 0.817. RPR level was correlated with clinical disease activity in SLE, and its value was normalized after treatment.

Conclusion: RPR may be a useful measurement for the assessment of disease activity in SLE patients.

Figure 1

Comparison of PLR, RPR, and MPV in SLE patients and healthy controls. (A) PLR level was significantly increased in SLE patients. (B) RPR level was significantly increased in SLE patients. (C) MPV was decreased in SLE patients (all P < .05). MPV = mean platelet volume, PLR = platelet-to-lymphocyte ratio, RPR = red blood cell distribution width-to-platelet ratio, SLE = systemic lupus erythematosus.

Figure 2

Comparison of PLR, RPR, and anti-dsDNA before and after treatment. All 3 indicators of SLE were reduced after treatment (P < .05). dsDNA = antidouble-stranded antibody, PLR = platelet-to-lymphocyte ratio, RPR = red blood cell distribution width-to-platelet ratio, SLE = systemic lupus erythematosus.

Figure 3

Correlation between SLEDAI and RPR, MPV, anti-dsDNA, and PLT in SLE patients. Spearman correlation analysis was performed to examine the association between SLEDAI and RPR, and other laboratory parameters. (A) RPR level was positively correlated with SLEDAI score. (B) MPV was positively correlated with SLEDAI score. (C) Anti-dsDNA was positively correlated with SLEDAI score. (D) PLT was negatively correlated with SLEDAI score (all P < .05). dsDNA = antidouble-stranded antibody, MPV = mean platelet volume, RPR = red blood cell distribution width-to-platelet ratio, SLE = systemic lupus erythematosus, SLEDAI = Systemic Lupus Erythematosus Disease Activity Index.

Figure 4

Receiver-operating characteristic (ROC) curves of RPR for the differentiation of SLE patients from healthy controls. RPR yielded a higher AUC than either PLR and MPV. MPV = mean platelet volume, RPR = red blood cell distribution width-to-platelet ratio, SLE = systemic lupus erythematosus.