Is blood neutrophil-lymphocyte ratio an independent predictor of knee osteoarthritis severity?

Knee osteoarthritis (OA) is one of the most common forms of joint disease, affecting an increasing number of people worldwide. Latest data suggests that inflammation plays a critical role in the pathogenesis of OA. There are a number of inflammatory markers like cytokins and cartilage degradation products that can be used as indicators in OA. Blood neutrophil-lymphocyte ratio (NLR) is a simple non-invasive and cost-effective marker of inflammation in various systemic diseases, but it has not been investigated in OA yet. The aim of the present study was to compare blood NLR levels in patients with severe - Kellgren and Lawrence (KL) grade 4 - knee OA and mild to moderate - KL grades 1-3 - knee OA. A total of 176 patients with knee OA were included in this cross-sectional study. KL grading was done according to the two-view (antero-posterior and lateral) plain radiography of both knees. Demographic characteristics, blood neutrophil, lymphocyte and platelet counts, erythrocyte sedimentation rate, and C-reactive protein were recorded. Blood NLR levels were calculated. In the severe knee OA group, blood NLR levels were found to be elevated as compared to the mild to moderate knee OA group. A blood NLR of ≥2.1 was taken as the cutoff based upon the receiver operating characteristics (roc). In the roc curve analysis, blood NLR ≥ 2.1 had 50 % sensitivity and 77 % specificity in predicting severe knee OA. In multivariate analysis, age and blood NLR ≥ 2.1 emerged as independent predictors of severe knee OA. The results of the present study, for the first time in the literature, suggests blood NLR as a novel and promising inflammatory marker indicating the severity of knee OA.