Z-scores, the number of standard deviations (SD) from the normal mean for age and gender, were calculated using selleck compound matched 10-year cohorts of a Dutch reference group (150 men or 350 women), checked for serum 25OHvitD levels >50 nmol/L as well as for lumbar spine and hip BMD T-score >−2.5 after 50 years of age. BMD measurement BMD of lumbar spine (anterior-posterior projection at L1–L4) and hip (total proximal femur) were measured using DXA (Hologic QDR Discovery (UMCG) or Hologic QDR Delphi (MCL), Waltman, MA, USA). According to the World Health Organization (WHO) classification, osteopenia was defined as a T-score TGF-beta inhibitor between −1 and −2.5 and osteoporosis as a T-score ≤−2.5 [34]. Patients were categorized by the lowest T-score

of the lumbar spine or hip. T-scores, the number of SD from the normal mean obtained from young healthy adults, were

calculated using the NHANES reference database. DXA measurements of lumbar spine and hip were available for 106 and 108 patients, respectively. Vertebral assessment Anterior, middle, and posterior heights of vertebrae T4 to L4 were measured on lateral radiographs by two independent observers using a ruler. According to the Genant classification, a vertebral fracture was defined based on reduction in anterior, MK-4827 research buy middle, and/or posterior height: grade 1, 20–25% reduction; grade 2, 25–40% reduction; and grade 3, >40% reduction [35]. In case of discrepancy between the two observers, a third independent observer measured vertebral height in order to confirm the presence or absence of a vertebral fracture. Radiographs were available for 106 patients. Statistical analysis Statistical analysis was performed with SPSS 16.0 software (SPSS, Chicago, IL, USA). Results were expressed as mean ± SD or median (range)

for parametric and nonparametric data, respectively. Pearson’s and Spearman’s correlation coefficients were used as appropriate to analyze the relationship between BMD, BTM, vitamin D, and clinical measures of disease activity and physical function. Predictor analysis for low BMD, defined as lumbar spine or hip BMD T-score ≤−1, was performed using univariate logistic regression and multivariate logistic regression with conditional stepwise Amoxicillin backward inclusion of variables that had a p value ≤ 0.3 in univariate analysis, together with variables that significantly correlated with lumbar spine or hip BMD T-scores. The probability of p for stepwise removal was 0.10. Predictor analyses for sCTX and OC Z-scores were performed using univariate linear regression and multivariate linear regression with backward inclusion of variables that had a p value ≤ 0.3 in univariate analysis, together with variables that significantly correlated with sCTX or OC Z-scores. The probability of F for removal was 0.10. p values ≤ 0.05 were considered statistically significant. Results Mean age of the 128 AS patients was 41.0 years (SD ± 11.1), median disease duration was 14 years (range 1–53), and 73% were male.