Red blood cell distribution width: a potential maker estimating disease activity of ankylosing spondylitis.

Ankylosing spondylitis (AS) is a autoimmune disease, early and accurate detection is vital for effective treatment. Very recently, a large of novel laboratory index were found to diagnose AS. However, the correlation between red blood cell distribution width (RDW) and AS has been poorly discussed in previous study. Then, our aim was to focus on the association between RDW and AS. AS patients without drugs treatments and healthy individuals were incorporated in our study. Laboratory parameters including RDW tests were conducted consecutively on the entire cohort of AS patients and healthy individuals. AS patients with increased RDW showed significant difference compared to healthy individuals (13.66±0.77 vs. 12.77±0.47, P<0.01), similarly, difference of AS patients and heathy individuals stratified by sex was almost the same as that in two groups. Some significantly positive correlation were observed between RDW and CRP, ESR, IgG, BASDAI score in patients with AS (r=0.356, P=0.018; r=0.481, P=0.001; r=0.385, P=0.010; r=0.586, P<0.01), almost identical results were showed when AS patients was stratified by gender. Finally, receiver operating characteristic (ROC) curves of RDW levels to identify AS patients exhibited a statistically significant level (area under the curve of 0.853; sensitivity of 72.7%, specificity of 81.4%). The results suggested that increased RDW was associated with AS and may be used as a potential marker estimating disease activity of AS.