Rheumatoid arthritis (RA) is a chronic inflammatory condition that can be associated with abnormal bone turnover and hence osteoporosis. Osteocalcin (OC) levels are increased in conditions with high bone turnover, including high RA disease activity. Thus, OC levels could possibly be used as a marker to assess bone health and disease activity in RA patients. As there have been no previous studies looking at serum OC levels in Malaysian RA patients, this study was performed to examine possible correlations between OC, bone mineral density (BMD) and disease activity in this population. A cross-sectional study of 75 female RA patients and 29 healthy controls was performed. Serum OC was measured using a Quantikine® ELISA kit. Dualenergy x-ray absorptiometry (DXA) was used to assess BMD. Serum OC levels were not significantly different between RA patients (median 14.44 ng/mL, interquartile range [IQR 12.99]) compared to healthy controls (median 11.04 ng/mL IQR 12.29) (p=0.198). Serum OC increased with age (Spearman’s rho r=0.230, p=0.047). There was no significant correlation between serum OC and body mass index (BMI), menopause status, BMD, DAS28, swollen or tender joint counts. Overall, there were 11 (14.7%) patients with osteoporosis and 27 (36.0%) with osteopenia. Menopause status was significantly associated with BMD at all sites (lumbar spine p=0.002, femoral neck p=0.004, total hip p=0.002). Serum OC were similar in RA patients compared to healthy controls. In RA patients, serum OC did not correlate with RA disease activity or BMD. Menopause status remains an important influence on BMD. Thus, measuring serum OC levels in Malaysian RA patients was not useful in identifying those at risk of low BMD.
Study site: Rheumatology clinic, Hospital Tuanku Jaafar, Seremban, Negeri Sembilan, and Klinik Pakar Puchong, Kuala Lumpur, Malaysia
AIM: Vitamin D3 [25(OH)D] has been shown to be important in bone health and can influence rheumatoid arthritis (RA) disease activity. Vitamin D-binding protein (VDBP) levels vary with race and may modulate 'bioavailable' levels of 25(OH)D. The aim of this study was to explore the relationships between 25(OH)D, VDBP and clinical factors on bone mineral density (BMD) in a group of multi-ethnic Malaysian RA patients and healthy controls.
METHODS: A cross-sectional study of 77 female RA patients and 29 controls was performed. Serum 25(OH)D was measured using the Elecsys® Vitamin D total assay. Serum VDBP was measured using a Quantikine® enzyme-linked immunosorbent assay kit. BMD was assessed using dual-energy X-ray absorptiometry (DXA).
RESULTS: Overall, mean 25(OH)D levels were 42.66 ± 21.75 nmol/L with no significant difference between RA patients and controls. 25(OH)D levels were significantly higher in Chinese, compared to Malay/Indian subjects. In RA patients, menopausal status and body mass index (BMI) were significantly associated with BMD but not 25(OH)D or RA Disease Activity Score of 28 joints (DAS28). There was no significant correlation between 25(OH)D and DAS28, even after correction for menopausal status and BMI. VDBP levels were not significantly different between the races and did not significantly correlate with BMD, 25(OH)D overall, or DAS28 in RA patients.
CONCLUSIONS: In Malaysian RA patients, menopausal status and BMI were more important influences on BMD than 25(OH)D or RA disease activity. The utility of measuring VDBP levels in this population remains uncertain.
Study site: Rheumatology clinic, Hospital Tuanku Jaafar, Seremban, Negeri Semblance; Klinik Pakar Puchong, Puchong, Kuala Lumpur, Malaysia
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 enzyme-linked 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.