Platelet distribution width as a novel indicator of disease activity in systemic lupus erythematosus

Abstract

Background: Significance of platelet distribution width (PDW) and mean platelet volume (MPV) in assessing disease activity of systemic lupus erythematosus (SLE) remains unclear. This study was aimed to evaluate PDW and MPV as potential disease activity markers in adult SLE patients.

Materials and methods: A total of 204 study participants, including 91 SLE patients and 113 age- and gender-matched healthy controls, were selected in this cross-sectional study. They were classified into three groups: control group (n = 113), active SLE group (n = 54), and inactive SLE group (n = 37). Demographic, clinical, and laboratory data were analyzed.

Results: In patient group, PDW was statistically higher than that in control group (13.54 ± 2.67 vs. 12.65 ± 2.34, P = 0.012), and in active group, PDW was significantly increased compared to inactive group (14.31 ± 2.90 vs. 12.25 ± 1.55, P < 0.001). However, MPV was significantly lower in SLE group than in control group (10.74 ± 0.94 vs. 11.09 ± 1.14, P = 0.016). PDW was positively correlated with SLE disease activity index (P < 0.001, r = 0.529) and erythrocyte sedimentation rate (P = 0.002, r = 0.321) and negatively correlated with C3 (P < 0.001, r = -0.419). However, there was no significant association between MPV and these study variables. A PDW level of 11.85% was determined as a predictive cutoff value of SLE diagnosis (sensitivity 76.9%, specificity 42.5%) and 13.65% as cutoff of active stage (sensitivity 52.6%, specificity 85.3%).

Conclusion: This study first associates a higher PDW level with an increased SLE activity, suggesting PDW as a novel indicator to monitor the activity of SLE.

Keywords: Biomarkers; blood platelets; systemic lupus erythematosus.

Figure 1

PDW and MPV of SLE patients with varying disease activities and controls. (a) The PDW values of SLE patients (n = 91) were significantly higher than those of controls (n = 113; P = 0.012). (b) The MPV values of SLE patients (n = 91) were significantly lower than those of controls (n = 113; P = 0.016). (c) A significant difference in PDW was observed between patients with active and those with inactive SLE (P < 0.001). (d) No significant difference in MPV was observed between patients with active and those with inactive SLE. PDW = Platelet distribution width; MPV = Mean platelet volume; SLE = Systemic lupus erythematosus

Figure 2

Relative analysis of SLEDAI, ESR, and C3 with PDW. The number of SLE patients was 91. Each point represents one pair of data (x and y value). There were significant positive and linear associations of (a) SLEDAI (P < 0.001, r = 0.529) and (b) ESR (P = 0.002, r = 0.321) with PDW. (c) Significant negative and linear association of C3 titters with PDW was observed (P < 0.001, r = −0.419). SLEDAI = Systemic lupus erythematosus disease activity index; ESR = Erythrocyte sedimentation rate; C3 = Complement 3; PDW = Platelet distribution width; SLE = Systemic lupus erythematosus

Figure 3

PDW and MPV of different clinical cutaneous manifestations. Significant difference of PDW values between (a) rash and no rash (14.72 ± 3.18 vs. 12.53 ± 1.56, P < 0.001), (c) alopecia and no alopecia (16.10 ± 3.57 vs. 13.15 ± 2.29, P = 0.016), (e) mucosal ulcer and no mucosal ulcer patients (14.38 ± 3.03 vs. 12.42 ± 1.50, P < 0.001) was shown. But no evident difference of MPV values between (b) rash and no rash (10.75 ± 1.10 vs. 10.73 ± 0.78, P = 0.926), (d) alopecia and no alopecia (10.37 ± 1.25 vs. 10.79 ± 0.88, P = 0.273), (f) mucosal ulcers and no mucosal ulcers (10.88 ± 1.04 vs. 10.55 ± 0.75, P = 0.076) was obtained. PDW = Platelet distribution width; MPV = Mean platelet volume

Figure 4

ROC analysis for PDW. (a) The ROC/AUC analysis of PDW values as diagnosis markers of SLE demonstrated a sensitivity of 76.9% and a specificity of 42.5% (AUC = 0.613; 95% CI, 0.535–0.690) when a cutoff value of 11.85% was used for PDW (P = 0.006). (b) It was also revealed that PDW for predicting activation of SLE was 13.65% (AUC = 0.710; 95% CI, 0.606–0.814) with a sensitivity of 52.6% and a specificity of 85.3% (P = 0.001). ROC = Receiver-operating characteristics curve; PDW = Platelet distribution width; AUC = Area under curve; SLE = Systemic lupus erythematosus; CI = Confidence interval