Background: To evaluate bone metabolism in patients with ankylosing spondylitis (AS) and test the hypothesis that nitrite, fetuin A with vitamin D and TNF-α serum concentrations are correlated with the severity of bone loss as assessed by bone mineral density (BMD) and biochemical markers of bone turnover. Osteoporosis occurs frequently in patients with AS and OPG represents a soluble decoy receptor that neutralizes receptor activator of nuclear factor-κB ligand (RANKL), an essential cytokine for osteoclast function. Materials and Methods: In our study, patients with ankylosing spondylitis (AS) who were visiting or admitted in the OPD and Emergency departments of Mahavir Institute of Medical Sciences, Vikarabad were formally enrolled for this study. Clinical data, radiographs of the spine, BMD of lumbar spine and the femur, biochemical markers of bone turnover, and serum levels of feutin A, nitrite were evaluated in 60 patients with AS (72% men) and 60 age-matched healthy controls (76% men). The estimation and comparison in serum biomarkers' levels have been analysed in concern with their ability to predict impaired healing at an early stage. All this consolidated data was analysed using SPSS software. Results: The result showed significant variations in measuring haemoglobin (Hb), Serum nitrite but significant increase of white blood cells (WBCs), platelets count and erythrocyte sedimentation rate (ESR) with increasing of TNF-α (P value<0.01) among different group. Conclusions: From the result can be accomplish that fetuin A with vitamin D and TNF-α play essential role in prognosis and aetiology of AS. Thus, measurements of these biomarkershold promise in differentiating between inflammatory and mechanical low back pain.