Clinical usefulness of measuring red blood cell distribution width in patients with systemic sclerosis

Red blood cell distribution width (RDW) is a biomarker quantifying the variability of red blood cell size in peripheral blood. Elevated RDW has been found to be an independent prognostic factor for cardiovascular events. SSc is characterized by generalized micro- and macroangiopathy. Our aim was to investigate RDW as a potential biomarker for the assessment of the severity of vascular involvement.

One hundred and sixty-eight consecutive SSc patients--62 with dcSSc and 106 with lcSSc--were investigated at baseline and after 1-year of follow-up. Measurements in 93 patients with primary RP and 40 healthy subjects served as controls.

The median RDW value of patients with SSc was higher [14.2% (25th-75th percentiles 13.5-14.8%) compared with the group of primary RP patients [13.9% (13.4-14.4%); P < 0.05) and healthy volunteers [13.6% (13.2-13.8%; P < 0.01]. dcSSc and anti-topoisomerase antibody-positive cases showed elevated RDW values compared with lcSSc and anti-topoisomerase antibody-negative cases (P < 0.05). RDW showed a positive correlation with inflammatory markers, including ESR (P < 0.05) and CRP (P < 0.05), and a negative correlation with forced vital capacity (P < 0.05) and diffusing capacity of the lung for carbon monoxide (DLCO) (P < 0.05) during the follow-up. An increase in RDW of >5% during follow-up was associated with an average 8.9% decrease in left ventricular ejection fraction (LVEF) and 7% in DLCO and these associations were independent of each other.

RDW in SSc may represent an integrative measure of multiple pathological processes including extensive vasculopathy, fibrosis or ongoing inflammation. An increase in RDW may indicate an impairment of cardiorespiratory function.