Epidemiology of vitamin D deficiency in West African hemodialysis patients: A pilot study from Senegal

Mineral bone disorder and osteoporosis in hemodialysis patients

BACKGROUND

Bone disease is common in patients undergoing hemodialysis. It is the result of bone turnover abnormalities and the decrease of bone mineral density (BMD). We aimed to determine the usefulness of serum bone turnover markers and BMD measurement by dual-energy x-ray absorptiometry (DXA) in hemodialysis patients.

METHODS

We conducted a cross-sectional study including 90 hemodialysis for more than 12 months. Bone mineral density was assessed by DXA. Peripheral blood samples were obtained from each patient before dialysis in a fasting state within a week of the DXA. Biochemical variables of calcium and phosphate were measured. One bone formation marker (bone-specific alkaline phosphatase (bAP), one bone resorption marker (carboxy-terminal telopeptides of type 1 collagen (CTX)) were measured. Total alkaline phosphatase (TAP), intact parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) which is a bone-derived hormone were also measured.

RESULTS

CTX values were 6.25 times higher than the normal limit of the assay. Bone alkaline phosphatase levels were less than 10 ng/mL in 28.8% of cases. 23% of patients have osteoporosis and 45% have osteopenia. Femoral BMD had negative correlations with age and PTH levels. FGF23 levels were significantly increased in patients with osteoporosis affecting the lumbar. The levels of bAP and CTX showed a positive correlation. Both circulating bAP and CTX levels showed also positive correlations with PTH levels. Fractures, observed in 12.2% of cases, were associated with low PTH values and the existence of osteoporosis.

CONCLUSIONS

Our study showed that osteoporosis and fracture are common in dialysis patients. The reduced BMD was associated with advanced age and elevated levels of PTH. Markers of bone turnover and FGF23 may play a role in the diagnosis of bone disease in hemodialysis patients. DXA measurement is necessary for the monitoring for bone loss.

Vitamin D, bone alkaline phosphatase and parathyroid hormone in healthy subjects and haemodialysed patients from West Africa: impact of reference ranges and parathyroid hormone generation assays on the KDIGO guidelines

BACKGROUND

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend targets based on multiples of the upper limit of normal (ULN) of parathyroid hormone (PTH) concentration. However, the ULN has not always been correctly established by manufacturers. While it is known that the ULN is supposed to be higher in African Americans than in Caucasians, it is largely unknown in Africans.

METHODS

We established the ULN of PTH concentration in a population of 240 healthy Ivorians using second- and third-generation PTH assays before and after supplementation with 100 000 IU of cholecalferol. We measured the levels of PTH, bone alkaline phosphatase, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in 100 haemodialysed Ivorian patients.

RESULTS

The prevalence of vitamin D deficiency in Ivory Coast is low. The ULN obtained using the third-generation PTH assay was similar to that obtained in Caucasians but was higher when PTH was measured using the second-generation PTH assay. According to the KDIGO guidelines, ∼20% of the haemodialysed patients were below twice the ULN and 30% were above nine times the ULN. Approximately 25% of the patients were even >12 times the ULN. We observed a discrepancy in the results between the two PTH assays (14%) that was relatively more important than what we observed from previous studies in Caucasians using the same strategy.

CONCLUSIONS

We found a low prevalence of vitamin D deficiency in a tropical country like Ivory Coast. We also established the PTH reference range, which could prove useful for the follow-up of haemodialysed patients, particularly for the large number of patients suffering from secondary hyperparathyroidism who are at high risk of adverse bone events.