Elevated monocyte distribution width in patients with active adult-onset Still's disease: a novel activity indicator.

Abstract

Monocyte distribution width (MDW) correlates with volume modifications of circulating monocytes upon activation. Given the crucial role of monocyte activation in the pathogenesis of adult-onset Still's disease (AOSD), we aimed to examine the associations between MDW and disease activity or inflammatory parameters in this disease. In 58 AOSD patients and 95 other patients with coronavirus disease 2019 (COVID-19) as disease control, MDW and complete blood count were determined using a UniCel DxH800 analyser. C-reactive protein (CRP) levels were measured by nephelometry, and ferritin levels by chemiluminescent immunoassay. AOSD activity was assessed using a modified Pouchot score. MDW was significantly higher in active AOSD patients (median 28.3, interquartile range [IQR] 23.3-32.1) compared with inactive AOSD (19.2, IQR 18.0-20.6, p<0.001) or non-severe COVID-19 patients (23.2, IQR 21.0-25.2, p<0.01). MDW was positively correlated with AOSD activity scores, CRP, and ferritin levels (all p<0.001). Longitudinal follow-up evaluation revealed that median MDW significantly declined (28.3 versus 18.5, p<0.001) along with disease activity, paralleling a decrease in CRP and ferritin levels. Severe COVID-19 and sepsis patients had elevated MDW, which were not different from active AOSD patients. Multivariate analysis revealed MDW as a significant predictor of active AOSD, and MDW threshold at 21.7 could predict an active status with a high sensitivity of 91.3% and specificity of 94.3%. Elevated MDW and its positive correlation with inflammatory parameters in AOSD patients indicate MDW as a novel activity indicator, with a high MDW value above 21.7 linked to a high probability of active AOSD.