Treatment of secondary hyperparathyroidism in hemodialysis patients: a comparison between two Italian centers to evaluate real-world guideline implementation

Background: Even though calcimimetics and active vitamin D are frequently used, studies using data from dialysis Registries have shown a progressive increase in parathyroid hormone (PTH) levels in the dialysis population over the last 20 years. In the relatively small sample of Italian patients included in the DOPPS phase 5 (n = 449), elevated or suppressed PTH levels were observed in 14% and 34% of patients, respectively. The aim of this study was to assess mineral metabolism parameters and treatment strategies in the hemodialysis population of two Centers in Northern Italy. Methods: We included all chronic hemodialysis patients treated between September and October 2023 at the Dialysis Centers of Cremona (n = 177) and Brescia (n = 315). Both Dialysis Units followed the KDIGO guidelines. However, differences in treatment strategies were noted. Patients in Brescia were systematically prescribed 25-OH vitamin D, while in Cremona, if 1-25 vitamin D was prescribed, 25-OH vitamin D was discontinued. In the Brescia Center, all patients used a 1.50 mmol/l calcium dialysate concentration, while in Cremona patients with hypercalcemia or suppressed PTH levels were prescribed a 1.25 mmol/l calcium dialysate concentration. Mineral metabolism parameters were evaluated and compared to KDIGO recommendations in both settings. Results: In the hemodialysis population considered, the prevalence of high (> 600 pg/ml) or suppressed (< 150 pg/ml) PTH levels was, 8.1% and 24%, respectively. Patients treated at the Brescia Center had significantly lower serum calcium and phosphate levels as compared to patients treated in Cremona. However, serum PTH and 25-vitamin D levels were higher in Brescia. In Brescia, native vitamin D was prescribed more frequently than in Cremona (81.9% vs 5.1%, p < 0.001). In Cremona, both active vitamin D and calcimimetics were prescribed more frequently than in Brescia (respectively, 62.1% and 50.9% vs 39.7% and 27.2%, p < 0.001). The prevalence of hypercalcemia (Brescia: 1.6%, Cremona: 1.7%), hypocalcemia (Brescia: 19%, Cremona: 16%), hyperphosphatemia (Brescia: 35%, Cremona: 40%), and elevated PTH levels (Brescia: 7.6%, Cremona: 9.0%) did not differ significantly. Suppressed PTH levels were more frequent in patients treated in Cremona (35% vs 20%, p < 0.001). Conclusions: Our study found, in the two clinical settings of the study, a lower prevalence of patients with elevated or suppressed PTH levels compared to the Italian patients included in DOPPS. Despite different treatment strategies, the prevalence of elevated PTH levels was similar in the two Centers. This suggests that different therapeutic strategies may be equally effective in controlling secondary hyperparathyroidism.