On-line haemodiafiltration improves response to calcifediol treatment

25-hydroxy vitamin D (25-OH-vit D) levels in the blood are associated with multiple pathologies. "Normal" values have been defined based on cardiovascular risk, and under this framework, patients with chronic kidney disease often have a deficit. 25-OH-vit D replacement in patients on haemodialysis (HD), in which dosage has not yet been clearly established, is becoming a constant in our daily practice.

To assess whether dialysis technique influences the baseline concentration of 25-OH-vitamin D and the response to supplements.

Prospective observational study of two cohorts of patients, those patients treated with calcifediol and those untreated (controls). Blood levels of Ca, P, PTH, and 25-OH-vit D were measured in 59 prevalent patients on HD (35 male; mean age: 65.2 (15.7) years) in November 2010. Thirty-six patients with 25-OH-vit D<10 ng/ml were treated with weekly calcifediol (Hidroferol®, 1 ampoule: 266 μg) since January 2011, which was administered after HD by a nurse. They received 6 doses, and blood levels were measured again in March 2011. We compared the response based on the technique of HD (online haemodiafiltration [OL-HDF] vs HD).

Mean baseline values (n=59): 25-OH-vit D: 9.8 (7.0)ng/ml, Ca: 9.3 (0.5)mg/dl, P: 4.5 (1.4)mg/dl, and iPTH: 299 (224)pg/ml. There were no differences by age, sex, or dialysis technique (HD vs OL-HDF). Treated patients (n=36): 25-OH-vit D levels rose from 6.2 (3.4)ng/ml to 51 (22.9)ng/ml (P<.0001), without significant changes in Ca. Serum phosphate increased an average of 0.6 (1.4)mg/dl, from 4.4 mg/dl to 5mg/dl, (P=.015). PTH decreased an average of 85 (208)pg/ml (P=.023). In these patients, the indication for phosphate binders increased by an average dose equivalent of 0.47 (0.82)mg/dl (P<.001). The 13 patients under treatment with OL-HDF reached 25-OH-vit D levels significantly higher than the 23 treated on HD: 63 (21)ng/ml vs 43 (21)ng/ml (P=.011). Dual treatment with native and active Vit D was associated with significantly increased levels of P (P=.043). Untreated patients (n=23): 25-OH-vit D levels decreased from 15.3 (7.5)ng/ml in November to 11.1 (6.8)ng/ml in March (P<.01), without significant changes in P or PTH and without differences according to age. 25-OH-vit D levels declined in patients on HD (15) but not in patients on OL-HDF.

The patients on haemodialysis have low or very low baseline values for 25-OH-vit D. The response to treatment with calcifediol is good, with the most marked improvement occurring in patients on OL-HDF. Furthermore, 25-OH-vit D levels decreased in untreated patients, which was probably correlated with the lower sun exposure in winter. Some patients experienced an increase in phosphataemia despite increasing the dosage of phosphate binders, mainly in those receiving treatment with active vitamin D.