Aberrant serum parathyroid hormone, calcium, and phosphorus as risk factors for peritonitis in peritoneal dialysis patients

Abstract

Identifying modifiable risk factors of peritoneal dialysis (PD)-related peritonitis is of clinical importance in patient care. Mineral bone disease (MBD) has been associated with mortality and morbidity in end-stage kidney disease (ESKD) patients. However, its influence on PD related peritonitis due to altered host immunity remains elusive. This study investigated whether abnormal biomarkers of MBD are associated with the development of peritonitis in patients undergoing maintenance PD. We conducted a retrospective observational cohort study, analysing data derived from a nationwide dialysis registry database in Taiwan, from 2005 to 2012. A total of 5750 ESKD patients commencing PD therapy during this period were enrolled and followed up to 60 months or by the end of the study period. The patients were stratified based on their baseline serum parathyroid hormone (PTH) levels, calcium (Ca) levels or phosphorus (P) levels, respectively or in combinations. The primary outcome was the occurrence of first episode of peritonitis, and patient outcomes such as deaths, transfer to haemodialysis or receiving renal transplantation were censored. Peritonitis-free survival and the influence of PTH, Ca, P (individual or in combination) on the peritonitis occurrence were analysed. A total of 5750 PD patients was enrolled. Of them, 1611 patients experienced their first episode of peritonitis during the study period. Patients with low PTH, high Ca or low P levels, respectively or in combination, had the lowest peritonitis-free survival. After adjusting for age, sex and serum albumin levels, we found that the combinations of low PTH levels with either high Ca levels or low/normal P levels were significant risk factors of developing peritonitis. Abnormal mineral bone metabolism in maintenance PD patients with low serum PTH levels, in combination with either high Ca levels or low/normal P levels, could be novel risk factors of PD-related peritonitis.

Figure 1

Kaplan–Meier survival analysis demonstrated that patients with (A) low intact parathyroid hormone (B) low intact parathyroid hormone, combined with low calcium (C) low intact parathyroid hormone, combined with low phosphorus, had a worse peritonitis-free survival among all stratified groups, respectively.

Figure 2

Subgroup analysis revealed that patients with age more than 65-year-old have significantly higher risk for peritonitis occurrence than those less that 65-year-old in the subgroups of “Ca: Normal/iPTH: Low” and “P: Low/iPTH: Low”. Patients with hypoalbuminemia (serum albumin < 3.7 g/dL) have significantly higher risk for peritonitis occurrence than those without hypoalbuminemia in the subgroups of “Ca: Normal/iPTH: Low”, “Ca: High/iPTH: Low” and “P: Normal/iPTH: Low”.