Introduction: Low 25-hydroxyvitamin D [25(OH)D] levels have not been consistently associated with bone mineral density (BMD). It has been suggested that calculation of the free/bioavailable 25(OH)D may correlate better with BMD. We examined this hypothesis in a cohort of Malaysian women. Materials and Methods: A cross-sectional study of 77 patients with rheumatoid arthritis (RA) and 29 controls was performed. Serum 25(OH)D was measured using the Roche Cobas E170 immunoassay. Serum vitamin D binding protein (VDBP) was measured using a monoclonal enzymelinked immunosorbent assay (ELISA). Free/bioavailable 25(OH)D were calculated using both the modified Vermuelen and Bikle formulae. Results: Since there were no significant differences between RA patients and controls for VDBP and 25(OH)D, the dataset was analysed as a whole. Calculated free 25(OH)D by Vermeulen was strongly correlated with Bikle (r = 1.00, p < 0.001). A significant positive correlation was noted between measured total 25(OH)D with free/bioavailable 25(OH) D (r = 0.607, r = 0.637, respectively, p < 0.001). Median free/bioavailable 25(OH)D values were significantly higher in Chinese compared with Malays and Indians, consistent with their median total 25(OH)D. Similar to total 25(OH)D, the free/bioavailable 25(OH)D did not correlate with BMD. Conclusion: In this first study of a multiethnic female Malaysian population, free/bioavailable 25(OH)D were found to reflect total 25(OH)D, and was not superior to total 25(OH)D in its correlation with BMD. Should they need to be calculated, the Bikle formula is easier to use but only calculates free 25(OH)D. The Vermuelen formula calculates both free/bioavailable 25(OH)D but is more complex to use.
bone mineral density

Introduction: Ankylosing Spondylitis is a chronic rheumatic arthritis with specifically related to lumbar spine and femoral neck. The disease is more common in young men. Inflame and inactive condition of patients with Ankylosing Spondylitis leads to a low bone mineral density. Determining osteomalacia has clinical significance because of the relation to bone density.\r\n', u'Objectives: To study the prevalence of osteoporosis and osteopenia in Ankylosing Spondylitis and to investigate correlation between bone mineral density and age at the beginning of the disease, BASDAI, BMI\r\n', u'Subjects and methods:119 male patients with ankylosing spondylitis, mean age of 29.0 \xb1 10.8 as defined by New York criteria modified in 1984. Bone mineral density was measured at the lumbar spine and hip with Unigamma X ray - Plus. Results: 26.1 % of patients had lumbar spine osteopenia and osteoporosis, while 41.2% had femoral neck osteopenia and osteoporosis. The beginning of the disease was 22.1 \xb1 7.8 and had correlation with bone density in lumbar spine. Low BMI group had decreased bone density in lumbar spine and femoral neck (BMI < 18.5), (p=0.0001 and p=0,005, respectively). Patients with active disease had lower bone density than those with stable disease.\r\n', u'Conclusion: Ankylosing spondylitis patients have decreased BMD values at both the spine and femur. Bone mineral density at lumbar spine and femoral neck had correlation with the BMI, Bone mineral density at femoral neck had correlation with BASDAI. \r\n', u'
Ankylosing spondylitis ; Bone mineral density ; Osteoporosis ; DXA.