The relation between bone mineral density and bone turnover markers in ankylosing spondylitis patients / 中华风湿病学杂志

ABSTRACT

Objective To study the pathophysiology of ankylosing spondylitis (AS)-related osteoporosis by investigating the relation between bone mineral density (BMD) and bone turnover markers.Methods Fortysix AS patients were included in this study,including 35 male and 11 female patients.Twenty-five gender and age matched healthy subjects were served as the healthy control group.Informed consents were obtained from all subjects.BMD of lumbar spine (L2-4),fermoral neck and radius were tested using dual-energy X-ray absorption method.Data about BASDAi,ESR,Ig was collected.Bone formation markers including procollagen type Ⅰ N-terminal peptide (PINP) and osteocalcin (OC) were included for analysis,the formal was measured by radioimmunoassay and the later was measured by immunoradiometric assay and bone resorption marker.β-Crosslaps was measured by electrochemiluminescence immunoassay.Independent-samples t test was used to compare normal distributed data between the two groups.Analysis of variance was used to compare the data between the three groups.For those data which were not normally distributed,Rank sum test was performed.Correlations were determined by Pearson or Spearman's ranking.Results ① 48％ of AS patients had bone loss,while the percentage in the healthy control group was 20％ (x2=5.32,P=0.021).BMD of lumbar spine,fermoral neck and radius of the AS patients were lower than the controls (t=-3.73,-3.68,-5.24; P＜0.05).② Bone density (BMD) of lumbar spine in patients at the late stage was higher than patients at early disease stage (t=2.26,P=0.034),however,the BMD in the femoral neck was not.③ The procollagen (PINP),OC and β-CrossLaps were not significantly different in patients at different stage of diseases (P＞0.05).④BMD of lumbar spine was negatively correlated with the β-CrossLaps and ESR(r=-0.325,P=0.047; r=-0.314,P=0.046),The BMD in fermoral neck was negatively correlated with β-CrossLaps and OC (r=-0.387,P=0.024; r=-0.371,P=0.034),but they were not correlated with disease duration and BADSAI.Conclusion Osteoporosis is common in AS.Bone turnover markers including bone formation and bone resorption are increased in AS.β-CrossLaps is likely to predict bone loss in AS.