Vitamin D status and its association with mineral and bone disorder in a multi-ethnic chronic kidney disease population

BACKGROUND: Vitamin D deficiency is associated with secondary hyperparathyroidism and mineral and bone disorder (MBD) in chronic kidney disease (CKD). This study aimed to determine the prevalence of vitamin D insufficiency/deficiency, and the association between vitamin D status and MBD in a multi-ethnic CKD population in Southeast Asia.

METHODS: Predialysis CKD patients were included in this cross-sectional study. Patient demographics, medical/medication histories, and laboratory parameters (serum 25-hydroxyvitamin D (25(OH)D), creatinine, phosphate (P), calcium, albumin, and intact-PTH (i-PTH)) were collected and compared among patients with various CKD stages. The association between 25(OH)D and these parameters was determined by multiple linear regression.

RESULTS: A total of 196 patients with mean ± SD eGFR of 26.4 ± 11.2 mL/min/1.73 m2 was included. Vitamin D deficiency (25(OH)D concentration < 15 ng/mL) and insufficiency (25(OH)D concentration 16 - 30 ng/mL) was found in 29.1% and 57.7% of the patients, respectively. Mean ± SD serum 25(OH)D was 20.8 ± 9.3 ng/mL. Female patients had lower vitamin D concentrations than males (16.9 ng/mL vs. 23.9 ng/mL; p < 0.001). Vitamin D levels were also higher in Chinese (22.3 ng/mL) than Malay (17.3 ng/mL) and Indian (13.1 ng/mL) patients (p < 0.05). Nonadjusted analyses showed higher i-PTH concentration in vitamin D deficient patients (p < 0.05).

CONCLUSION: Despite being a sun-rich country all year round, the majority (86.8%) of predialysis CKD patients in Singapore have suboptimal vitamin D status. Lower vitamin D concentrations were found in females and in those with darker skin tone. Vitamin D deficient patients also tended to have higher i-PTH levels.