Third-generation parathyroid hormone assays and all-cause mortality in incident dialysis patients: the CHOICE study.
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.
Departments of Medicine and Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY, USA. mmelamed@aecom.yu.edu
Michal L
ML
Melamed
Joseph A
JA
Eustace
Laura C
LC
Plantinga
Bernard G
BG
Jaar
Nancy E
NE
Fink
Rulan S
RS
Parekh
Josef
J
Coresh
Zan
Z
Yang
Tom
T
Cantor
Neil R
NR
Powe
D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods* / Q000706:statistics & numerical data; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000209:etiology / Q000401:mortality; D007676:Kidney Failure, Chronic / Q000097:blood / Q000150:complications / Q000401:mortality / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000032:analysis* / Q000097:blood*; D010446:Peptide Fragments / Q000032:analysis / Q000097:blood; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D006435:Renal Dialysis / Q000009:adverse effects*
D010281:Parathyroid Hormone; D010446:Peptide Fragments; C414937:parathyroid hormone (7-84)