The role of lymphocyte-monocyte ratio on ankylosing spondylitis diagnosis and sacroiliitis staging  

Abstract Background: Ankylosing spondylitis (AS)is a chronic inflammatory disorder involving the sacroiliac joints, that could lead to disability due to the failure of timely treatment. Therefore, early diagnosis is essential to for AS treatment. The lymphocyte-to-monocyte ratio (LMR) is an indicator of disease progression. However, its role in AS remains unclear. The aim of this study was to investigate the role of LMR in AS diagnosis, disease activity classification and sacroiliitis staging. Methods: Seventy-eight AS patients and 78 sex and age matched healthy controls (HCs) were enrolled in this study. The diagnosis of AS was performed according to the New York criteria or the Assessment of SpondyloArthritis international Society (ASAS) classification criteria, whereas the staging of sacroiliitis in AS patients was determined by X-ray examination. Comparisons of LMR levels between groups were performed using t test. Pearson or Spearman correlation analysis were used to assess correlations between LMR and other indicators. Receiver operating characteristic (ROC) curves were used to determine the role of LMR in the diagnosis of AS. Results: Higher neutrophil-to-lymphocyte ratio(NLR), red blood cell distribution width(RDW), platelet-to-lymphocyte ratio(PLR), mean platelet volume(MPV), erythrocyte sedimentation rate (ESR), and C-reactive protein(CRP) levels and lower red blood cell (RBC), hemoglobin (Hb), Hematocrit (Hct), LMR, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL) and albumin/globulin (A/G) levels were noted in AS patients compared to HCs. Positive correlations were observed between LMR and RBC, Hb, Hct and A/G, whereas negative correlations were found between LMR and NLR, PLR, AST, and TBIL ( P< 0.05 ). ROC curves showed that the area under the curve(AUC) for LMR in the diagnosis of ankylosing spondylitis was 0.803 (95% CI =0.734-0.872) with a sensitivity and specificity of 62.8% and 87.2%, respectively, and the AUC (95% CI) for the combination of ESR, CRP and LMR was 0.975 (0.948-1.000) with a sensitivity and specificity of 94.9% and 97.4%, respectively. LMR levels were lower ( P<0.05 ) and significant differences in LMR values were observed among different stages (P<0.05). Conclusions: Our study suggested that LMR could be an important inflammatory marker that can be used to diagnosis AS and identify disease activity and X-ray stage of sacroiliitis.