This analysis showed that in maintenance hemodialysis patients with SHPT, severely affected patients, with iPTH ? 300 pg/mL and with high or low calcium levels (U shape), tended to have higher mortality rates, whereas in mildly affected patients with iPTH < 300 pg/mL, the mortality rates were higher only in patients with high calcium levels. Analysis by phosphate level showed that both severely and mildly affected patients with high phosphate levels had higher mortality rates; however, no significant difference was found with low phosphate levels.
With regard to the relationship between calcium levels and prognosis in hemodialysis patients, high calcium levels have consistently been shown to be associated with increased mortality rates [4,5,6,7]. Reports focusing on the relationship between calcium levels and prognosis depending on PTH level include those from the WW-DOPPS and United States Renal Data System (USRDS) studies. The WW-DOPPS study reported that patients with either high or low calcium levels had high mortality rates, both in the subpopulation with iPTH ? 300 pg/mL and that with iPTH < 300 pg/mL . A study by Block et al. using the USRDS assessed the relationship between calcium levels and mortality rates or combined events of death and cardiovascular hospitalization by iPTH level, showing that the risk increased with high calcium levels (? 10 mg/dL) compared with corrected calcium levels in the control target range (8.4–10.0 mg/dL) at all iPTH levels, but not showing any change in the risk with low calcium levels (< 8.4 mg/dL) .
With regard to the relationship between low phosphate levels and mortality, an exhaustive survey in Japan 7 showed increased risk of death with low phosphate levels (< 3
5 mg/dL) at all iPTH levels, and tended to increase with low calcium levels (< 8.5 mg/dL) in the iPTH ? 300 pg/mL stratum, but not in the < 300 pg/mL stratum. In the subpopulation with calcium levels < 8.5 mg/dL, patients with iPTH ? 300 pg/mL compared with those with iPTH < 300 pg/mL were characterized by shorter duration of hemodialysis, a higher proportion of untreated cases of VDRA, a higher male:female ratio, and a higher incidence of diabetic nephropathy. The aIRs for all-cause mortality and cardiovascular mortality in the subpopulation with iPTH ? 300 pg/mL and serum calcium < 8.5 mg/dL were more than double those in the subpopulation with iPTH < 300 pg/mL and serum calcium level < 8.5 mg/dL (Table S1). The poor prognosis for patients with iPTH ? 300 pg/mL and serum calcium < 8.5 mg/dL is attributable to any possible unmeasured confounding factors associated with the poor prognosis, as well as to the limitations on cinacalcet prescriptions and the inability to use VDRA optimally. Hypocalcemia may have strongly affected the worse prognosis in SHPT patients with iPTH ? 300 pg/mL and serum calcium < 8.5 mg/dL. In these patients, it seems necessary to use a calcimimetic and VDRA in combination in order to control mineral parameters appropriately.
With regard to the relationship between phosphate levels and prognosis in hemodialysis patients, this analysis, in line with previous studies [4,5,6,7], demonstrated increased mortality and Bi-Dating-Seiten cardiovascular deaths due to high phosphate levels. 5 mg/dL), whereas a study by Block et al. and a report by Fukagawa et al. from the MBD-5D study found no increased mortality rates due to low phosphate levels. In our study, the risk of death did not change with low phosphate levels (< 4.0 mg/dL) in either of the iPTH strata (? 300 pg/mL and < 300 pg/mL). The risks with low phosphate levels might be attenuated by multi-adjusted factors such as undernutrition and frailty, which patients with low phosphate levels have.