P1414THE PREDICTORS OF PARATHYROID HORMONE VARIABILITY IN HEMODIALYSIS PATIENTS

Background and Aims KDIGO Clinical Practice Guidelines suggest in hemodialysis (HD) patients using a dialysate calcium concentration between 1,25 and 1,5 mmol/L and maintaining serum intact parathyroid hormone (sPTH) levels in the range of approximately 2 to 9 times the upper normal limit for the assay. The aim of the study was to evaluate the predictors of PTH variability in HD patients over a 12 months period. Method The multicenter restrospective study encompassed 398 patients (256M and 142F) with the average age 59,64±13,29 years and the average HD vintage 78,63±64,26 months. Over a 12 months (M0-M12) period: serum calcium (sCa), serum phosphorus (sPi), serum alkaline phosphatase (sAPh), oral calcium-carbonate daily dose, oral calcitriol weekly dose, and dialysate Ca concentration (dCa) were monitored monthly, and sPTH at 6 months. According to PTH assay reference level (18,4-80,1 pg/ml) 3 groups of patients were categorized: patients with low sPTH<160, with target range sPTH =160-721, and with high sPTH>721. For statistical analysis chi-square test, analysis of variance with repeated measures and logistic regression analysis were performed by softver SPSS. Results Over a 12 months period the number of patients with low sPTH significantly decreased, but the number of patients with target range sPTH and high sPTH increased (Chi square=269,45; p<0.001). On the basis of overall pattern of sPTH fluctuation over a 12 months period six subgroups of patients were observed: consistently low in 20,6% of patients, consistently within the target range in 22,1%, consistently high in 14,07%, low-amplitude fluctuation with low and target range sPTH levels (LAL) in 31,4%, low-amplitude fluctuation with target range and high sPTH levels (LAH) in 10,55%, and high-amplitude fluctuation (HA) subgroup with low, target range and high sPTH levels in 1,25%. In 35 patients constantly hemodialyzed over a 12 months period with dCa=1,25 mmol/L due to high sCa the significant increase of sPTH (M0=797±657 vs M12=1030±740 pg/ml; p=0.001) and no significant changes of sCa (M0=2,44± vs M12=2,34± mmol/L; n.s.), sPi (M0=1,81±0,49 vs M12=1,68±0,49 mmol/L; n.s.), Ca-carbonate daily dose (M0=1,88±1,54 vs M12=2,22±1,53 g/d; n.s.) and calcitriol weekly dose (M0=0,84±1,38 vs M12=1,1±1,41 ucg/w; n.s.) were observed. In 24 patients constantly hemodialyzed with dCa=1,75 mmol/L due to low sCa the significant decrease of sPTH (M0=518±582 vs M12=391±530 pg/ml; p=0.037) and no significant changes of sCa (M0=2,17±0,19 vs M12=2,18±0,17 mmol/L; n.s.), sPi (M0=1,3±0,34 vs M12=1,36±0,52 mmol/L; n.s.), Ca-carbonate daily dose (M0=2,53±1,58 vs M12=2,1±1,91 g/d; n.s.) and calcitriol weekly dose (M0=1,33±1,23 vs M12=1,42±1,69 ucg/w; n.s.) were observed. In 195 patients constantly hemodialyzed with dCa=1,5 mmol/L no significant changes of sPTH (M0=388±421 vs M12=434±459 pg/ml; n.s.), sCa (M0=2,29±0,18 vs M12=2,27±0,15 mmol/L; n.s.), sPi (M0=1,48±0,41 vs M12=1,52±0,41 mmol/L; n.s.), Ca-carbonate daily dose (M0=2,42±1,4 vs M12=2,57±1,2 g/d; n.s.) and calcitriol weekly dose (M0=0,47±0,72 vs M12=0,38±0,68 ucg/w; n.s.) were observed. By model of logistic regression analysis dCa=1,75 (OR=8,33), increased sCa (OR=7,7), and presence of diabetes mellitus (OR=2,44) were the most significant predictors of low sPTH<160 (Chi square=116,27; p<0.001), but the increased sCa (OR=6,88), dCa=1,25 (OR=5,08), and the increased sPi (OR=2,72) were the most significant predictors of high sPTH>721 (Chi square=72,475; p<0.001). Conclusion The prolonged use of dCa=1,25 in patients with high sCa led to significant sPTH increase likely due to net negative calcium balance, but prolonged use of dCa=1,75 in patients with low sCa led to significant sPTH decrease likely due to net positive calcium balance.