NDT Advance Access published online on December 8, 2007
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfm849
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Third-generation parathyroid hormone assays and all-cause mortality in incident dialysis patients: the CHOICE study
1 Departments of Medicine and Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY 2 Department of Medicine, The Johns Hopkins University School of Medicine 3 Welch Center for Prevention, Epidemiology and Clinical Research, The Johns Hopkins University 4 Cork University Hospital, Cork, Ireland 5 The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 6 Scantibodies Laboratory, Santee, CA, USA
Correspondence and offprint requests to: Correspondence and offprint requests to: Michal L. Melamed, 1300 Morris Park Avenue, Ullmann 615, Bronx, NY 10461, USA. Tel: 718-430-2304; Fax: 718-430-8963; E-mail: mmelamed{at}aecom.yu.edu
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Abstract |
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Background. There has been controversy about the utility of new third-generation parathyroid hormone (PTH) assays measuring only 1–84 PTH, with few large studies comparing second- and third-generation PTH measurements in patients with ESRD.
Methods. We measured 1–84 PTH (‘biointact’ or ‘whole’ PTH) and total PTH (‘intact’ PTH) in a national cohort of 515 incident dialysis patients from banked frozen EDTA plasma (median follow-up, 35 months) and examined the accuracy of estimating 1–84 PTH from total PTH and the associations of these levels with patient characteristics and mortality.
Results. The 1–84 PTH and total PTH levels were closely correlated. Higher 1–84 PTH was associated with African-American race and higher serum phosphate and lower calcium levels. The percentage of total PTH represented by 1–84 PTH was, on average, 53%, but with a wide range (25–89%). Calculating 1–84 PTH from total PTH using a proposed standard conversion factor (54%) led to misclassification of 8% of the population compared with measured 1–84 PTH. In a multivariate Cox proportional hazards model for all-cause mortality, a 1–84 PTH value >160 pg/ml was associated with increased risk of mortality (HR = 1.62, 95% CI, 1.03–2.54) compared to a level of 80–160 pg/ml. Elevated total PTH, 7–84 PTH and the 1–84 PTH/7–84 PTH ratio were not significantly associated with mortality.
Conclusions. The 1–84 PTH and total PTH are highly correlated. Elevated 1–84 PTH was significantly associated with increased mortality, whereas total PTH did not reach statistical significance. Thus, although in other respect they are similar, there may be utility in measuring 1–84 PTH for its associations with mortality.
Keywords: clinical epidemiology; hyperparathyroidism; mortality risk; parathyroid hormone; PTH assays
Received for publication: 18. 5.07
Revision received 30.10.07.
Accepted in revised form: 4.11.07