Serum Sclerostin as a Biomarker of Disease Activity in Ankylosing Spondylitis in Correlation with Radiographic Imaging

Abstract Background Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease defined by the development of new bone in the spine, resulting in joint fusion and functional impairment. The role of sclerostin has been evaluated in AS pathogenesis to identify a possible link with bone formation. Objective Evaluating serum sclerostin level in AS patients and investigating the presence of any correlations with radiographic damage, disease activity and function. Patients and Methods A total of 20 patients diagnosed as ankylosing spondylitis according to Ankylosing Spondylitis International Society (ASAS) criteria were enrolled in addition to 20 healthy age matched control cases. All patients were subjected to skin, nail, hair, enthesitis, dactylitis, peripheral and axial joint examination. Also, assessment of disease activity was done by using Ankylosing Spondylitis Disease Activity Score, Bath Ankylosing Spondylitis Disease Activity Index and Bath Ankylosing Spondylitis Functional Index. Serum sclerostin level was measured in all cases and correlated with disease activity. Radiographs of the spine and pelvis performed within three months from the enrollment in the study were collected in all patients. Each radiograph was evaluated by an expert reader using the modified Stoke Ankylosing Spondylitis Spinal Score. Finally, MRI examinations for both sacroiliac joints and spine were performed. Results Positive correlation was noted between serum sclerostin level and both intermalleolar distance and cervical rotation. A negative correlation between serum sclerostin level and BASMI score. Hemoglobin and hematocrit levels were lower while ESR and CRP levels were higher among AS cases with significant correlations with serum sclerostin level. Negative correlation was reported between serum sclerostin level and SIJs SPARCC score, spine SPARCC score and total SPARCC score. Also, significant positive correlation was noted between mSASSS with BASMI score. Cutoff point ≤20 pmol/L had sensitivity 100% and specificity 100%. Conclusion Serum sclerostin was found to be an accurate biomarker with good discriminating power between ankylosing spondylitis cases and healthy control individuals. Finally, serum sclerostin is advised to be used as a routine, less invasive, cheap and valid biomarker in patients with ankylosing spondylitis.