The Relationship of Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio with Bone Mineral Density in adolescent girls suffering from anorexia nervosa

Introduction: Inflammation is supposed to be one of the factors contributing to decreased bone mineral density (BMD) in anorexia nervosa (AN). Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are simple and cost-effective inflammatory markers, well documented as indicators of postmenopausal osteoporosis. This study aimed to assess the relationships between these ratios and BMD in girls with AN. Materials and methods: Electronic records of 73 girls hospitalized for AN were analyzed retrospectively. The age range of study group was 12.56-17.67 years. BMD was assessed by dual-energy X-ray absorptiometry (DXA) and expressed as Z-scores according to lumbar spine (s-BMD) and total body (TB-BMD) sites. NLR and PLR were calculated according to complete blood count results. Patients were divided into four subgroups, according to the DXA results: normal (Z-score >-2.0, n=63), low s-BMD subgroup (Z-score ≤-2.0, n=10), normal TB-BMD group (Z-score >-2.0, n=45) and low TB-BMD subgroup (Z-score ≤-2.0, n=28). Results: In the low s-BMD subgroup there was observed a tendency to an increase of mean NLR, PLR and WBC values. Respective BMD Z-score values correlated significantly and negatively with PLR in low s-BMD (R=-0.892, p<0.001) and normal TB-BMD (R=-0.451, p=0.002) subgroups, while with NLR – only in normal TB-BMD subgroup (R=-0.685, p<0.001). In low s-BMD subgroup the PLR was shown to be a significant and independent predictor of s-BMD (β=-0.881, p<0.001). The PLR contribute to 77.6% of s-BMD Z-score variability (R2=0.776, p<0.001). In normal TB-BMD subgroup, the PRL and NLR levels were significant and independent predictors of TB-BMD (β=-0.352, p=0.004 and β=-0.450, p=0.001 and β=-0.339, p=0.005, respectively), and explained 44,4% of TB-BMD Z-score variability (R2=0.444, p<0.001). Conclusions: These results indicate that there is possibly a relationship between bone mass loss and inflammation expressed as NLR and PLR in adolescent girls suffering from AN. It seems that these connections may be dependent on the examined skeletal area. NLR and PLR, which are common indicators of morbidity and mortality in many malignancies and inflammatory chronic diseases, can also be useful in the evaluation of bone condition in adolescent females with AN. However, there is a need for further investigation in this field.