Comparison of T- and Z-score in identifying risk factors of osteoporosis in inflammatory bowel disease patients

Objective: Most studies have shown contradictory results regarding predictive factors of osteoporosis in inflammatory bowel disease (IBD). Since in these studies either T- or Z-scores has been used, our aim was to compare T- and Z-score in identifying risk factors of osteoporosis in IBD patients. Materials and methods: Bone density was measured by dual X-ray absorptiometry (DXA) at L2-L4 of the spine and femoral neck in 122 patients. Twenty-two clinical parameters were recorded prior to DXA and evaluated by univariate and multivariate analysis. Results: On multivariate analysis, cumulative steroid dose was a predictive factor of femoral neck T-score (p<0.001) and Z-score (p=0.001). Age was a predictive factor of femoral neck T-score (p<0.001). BMI was a predictive factor of femoral neck Z-score (p=0.03). None of the other 19 variables tested had any predictive value for bone density. Age ≥55 years was a risk factor of low femoral neck ∆-score (OR 5.08, 95% CI 1.90-13.57, p=0.001), as was cumulative dose of prednisolone ≥5 g (OR 3.41, 95% CI 1.50-7.73, p=0.004). Conclusions: There is a discordance of results depending on whether T- or Z-scores are used in analysis. Among 22 parameters, cumulative steroid dose and age proved to be the most important factors.