Bone density measurements As part of the standard medical follow-up of fracture patients, bone mineral density (BMD; g/cm2) of the lumbar spine (L2–L4), femoral neck, and total hip (trochanter
and neck) was assessed by DXA, using the cross-calibrated Hologic QDR 4500 Elite densitometer (Waltham, Massachusetts, USA). BMD T-score values were used to establish the presence or absence of osteoporosis (T ≤ −2.5) and osteopenia (T < −1 to −2.5). T-score values were calculated using sex specific data from Dutch references. Statistical analysis Deviation of genotype frequencies from those expected under Hardy–Weinberg equilibrium was tested in the non-osteoporotic subjects (i.e. subjects with T-score value greater than −2.5) by the χ 2 test. Pairwise linkage disequilibrium (LD) between all SNPs was calculated using Haploview
v4.0. Descriptive statistics BAY 63-2521 were used to determine the prevalence of osteoporosis and osteopenia in the cohort of fracture patients, to assess distributions of possible risk factors, including sex, age (in years), body mass index (BMI, in kg/cm2), previous fracture (yes/no) and family history of fractures (yes/no), and to describe the ARS-1620 occurrence of different fracture types. Other possible risk factors for osteoporosis, such as vitamin D intake, calcium intake, years since menopause and physical activity could not be assessed, since we did not have access to reliable information on these factors. The software package PLINK was used to test for association between genetic variations
and BMD after testing for normal distribution click here of the data and uniformity of variances using SAS, version 9.1. Preliminary analyses showed that only sex, age and BMI were associated with several SNPs. Therefore all analyses were adjusted for age, sex and BMI. Furthermore, we performed analyses stratified by sex. All analyses include both traumatic and non-traumatic fractures. Both single SNPs and haplotypes were tested for association. As a confirmatory approach, we used proportional odds logistic Staurosporine nmr regression to estimate the influence of P2RX7 genotypes on the odds of a low BMD T-score value, and thus on osteoporosis risk. For this approach, quintiles of the population were defined based on BMD T-score values. The proportional odds assumption was tested using the chi-square score test. Again, analyses were performed for the total population as well as stratified by sex. This was done by the use of SAS, version 9.1. For all analyses, p values lower than 0.05 were considered statistically significant. Results Study population Of the 630 patients with a recent fracture who were invited to the osteoporosis outpatient clinic between August 2008 and December 2009, 467 (74.1 %) were willing to undergo bone densitometry. Of these, during their second consultation at the osteoporosis outpatient clinic, 394 (84.4 %) were willing to donate blood. The collection of blood failed for 13 (3.