New data demonstrate an association between lower levels of non-oxidized biologically active parathyroid hormone and increased mortality in hemodialysis patients, suggesting the need for improved assays.
“The current tests for parathyroid hormone levels overlook a key factor. When parathyroid hormone interacts with oxygen under conditions of stress such as end-stage kidney disease, it becomes biologically inactive,” researcherBerthold Hocher, MD, PhD, of the University of Potsdam in Germany, said in a press release.
Researchers conducted a prospective cohort study of 340 hemodialysis patients (224 men, 116 women; median age, 66 years) with end-stage CKD. They measured parathyroid hormone (PTH) levels using a third-generation intact parathyroid hormone electrochemiluminescence immunoassay system (ECLIA; Roche iPTH, Roche Diagnostics) directly and after prior removal of oxidized biologically inactive PTH using an antihuman oxidized parathyroid monoclonal antibody (Immundiagnostik AG).
During 5-year follow-up, 50% of the patients died. Cardiovascular diseaseaccounted for 60% of the deaths, according to the researchers, followed by infections (23%), cancer (11%) and unknown causes (6%).
Results revealed higher median non-oxidized biologically active PTH levels in those who survived (7.2 ng/L) vs. those who did not (5 ng/L; P=.002).
Survival was increased among patients in the highest tertile of non-oxidized biologically active PTH compared with the lowest (P=.0008). Additionally, in the highest tertile, median survival was 1,702 days compared with 453 days in the lowest tertile.
Data also showed that, after multivariable adjustment, older age appeared to increase risk for death, but higher levels of non-oxidized biologically active PTH decreased risk for death.
In an analysis of a subgroup of patients with intact PTH levels above the upper normal range of 70 ng/L at baseline, mortality appeared to be associated with oxidized biologically inactive PTH levels but not non-oxidized biologically active PTH levels.
“With more precise parathyroid hormone testing, health care professionals will have the information they need to improve clinical outcomes,” Hocher said. “The nephrology community has long recognized there is an issue with current testing approaches, and now we can solve this problem and improve patient care.”