FP617
ROLE OF VITAMIN D SUPPLEMENTATION IN HEMODIALYSIS (HD): A 1-YEAR PROSPECTIVE STUDY

INTRODUCTION AND AIMS: Previous studies have reported that hypovitaminosis D (vitamin D deficiency <20ng/mL and insufficiency 20-29ng/mL) is highly prevalent in patients in HD. KDOQI and KDIGO experts recommend checking and supplementing low serum 25(OH)D levels in chronic kidney disease and HD patients. The current study was conducted to evaluate the effect of oral Cholecalciferol supplementation in HD sessions.

METHODS: 12-month prospective study. Patients were supplemented with 12000 IU Cholecalciferol 3 times a week if vitamin D level was under 30ng/mL and 4000 IU if it was above. Every 6 months (3 time points: 1, 2 and 3) vitamin D, Bone Alkaline Phosphatase (BAP), Calcium (Ca²⁺), Phosphorus (P⁺) and intact Parathyroid hormone (iPTH) blood levels were analyzed. Data collected comprised demographic information, HD information, lab results, darbepoetin-α dose and diabetic status. Statistical analysis was performed using SPSS version 23 for Mac OS X.

RESULTS: From the 108 initial patients, only 44 patients completed the 12-month follow-up period: 65.9% (n=29) were males, medium age was 74.512.6 years, average HD time at time point 1 was 3.94.4 months and 38.6% (n=17) were diabetic. At time point 2, 23% (n=7) achieved a vitamin D blood level ≥30ng/mL however, at time point 3 (12^th month) no patient had vitamin D ≥30ng/mL. A repeat measures ANOVA demonstrated that vitamin D increased 11.5ng/mL (F=93.8, p=0.001) from time point 1 to 2 and decreased 2.3ng/mL (F=4.9, p=0.033) from time point 2 to 3. The same analysis, excluding patients with a vitamin D blood level ≥30ng/mL in time point 2, showed that vitamin D levels did not vary with time, diabetes (DM) or gender. However, in the 7 patients whose vitamin D dose had been changed, there was an average reduction of 11.7ng/mL (F= 28.8, p=0.002). iPTH and Ca2+ changed throughout time (repeat measures ANOVA: p=0.041, p=0.001), however those changes were not associated to vitamin D level variation. On the other hand, P+ suffered a reduction from time point 2 to 3 (-0.4mmol/L, F=4.9, p=0.033) and Pearson’s correlation confirmed those observations with a moderate positive correlation between vitamin D and P+ (time point 1 to 2: r=0.4, p=0.003; time point 2 to 3: r=0.5, p=0.002) DM influenced vitamin D concentration between the different analysis times, post hoc tests confirmed that the absence of DM has a higher impact in vitamin D levels (time point 1: 14.6ng/mL vs 6.7ng/mL, F=13.8, p=0.01) A Spearman’s rank-order correlation was run to determine the relationship between HD time at time point 1 and vitamin D levels. A weak positive correlation was verified (time point 2: r_s=0.34, p=0.027; time point 3: r_s=0.35, p=0.021).

CONCLUSIONS: Time, DM and HD time were associated with vitamin D blood levels. Despite small P⁺ variations during the study period, P⁺ also seems to be related with vitamin D, contrary to BAP, iPTH and Ca²+, where no association was found. Our results lead to the conclusion that 4000 IU 3 times a week is not sufficient to maintain vitamin D at normal levels. It is important to mention that we did not have in consideration the use of medication interfering in the phosphocalcic metabolism. Since we have a hospital HD facility, it is difficult to maintain all the enrolled patients until the end of the study. Our patients are also older and have more comorbidities, so it is likely that they have less solar exposure than the average hemodialysis population.