Statistical analysis
Continuous variables were summarized using descriptive statistics presented as mean and standard deviation (SD). Categorical variables were summarized using counts and percentages. Categorical data were analyzed using the Chi-square (χ2) test or Fisher exact test appropriately. Student’s t-test and analysis of variance were used for parametric variables.
A multiple regression analysis was performed to define the relationship between vertebral fractures and the following variables: age, gender, duration of chronic renal failure (CRF), duration of hemodialysis, time from renal transplantation, BMI, creatinine, PTH, creatinine, lumbar spine BMD, lumbar spine Z score, femoral neck BMD, and femoral neck Z score.
Two different multiple regression analyses were also performed to determine the relationship between lumbar BMD and femoral neck BMD and parameters. Age, gender, duration of CRF, duration of hemodialysis, time from renal transplantation, BMI, creatinine, PTH, creatinine, and 25-OH vitamin D were used as independent variables.
Multiple regression analysis parameters with a possible influence on PTH were added as covariates; age, gender, duration of CRF, BMI, calcium, phosphorous, and 25-OH vitamin D.
The results were evaluated at a 95% confidence interval, and p <0.05 was considered statistically significant. All statistical analyses were performed using software (GraphPad InStat 3.0; GraphPad Software, Inc., San Diego, CA, USA).