Serum intact parathyroid hormone and ionised calcium concentration in children with renal insufficiency.
We report our experience of the use of an immunoradiometric assay for intact parathyroid hormone (i-PTH) and the measurement of plasma ionised calcium concentration (PCa2+) in 73 children with chronic renal insufficiency (CRI); plasma creatinine concentration (PCr) 52-856 mumol/l. There was a poor correlation between i-PTH and PCr (r = 0.10, n = 552) compared with that for C-terminal PTH and PCr (r = 0.60, n = 248), suggesting that the i-PTH assay is independent of renal function in this group of treated children. A clear response of i-PTH to a low total plasma Ca (tPCa) and PCa2+ was observed. There was a significant positive correlation between both tPCa and PCa2+ (r = 0.50, n = 389) and the fraction of Ca2+ (the fraction of tCa which was ionised) and PCa2+ (r = 0.50, n = 389). The finding of a low or normal PCa2+ with a low calculated fraction of Ca2+ was frequently observed, i.e. the measured tPCa was unexpectedly high, suggesting complexing of Ca2+ by accumulated anions in CRI. There was a poor relationship between the plasma albumin concentration and both bound plus complexed Ca (tPCa minus PCa2+) and the fraction of Ca2+ (r = 0.15 and -0.17, respectively). The positive predictive value for a raised i-PTH of a tubular reabsorption of phosphate of less than 80% was 0.87, and of an alkaline phosphatase greater than 800 U/l was 0.37.(ABSTRACT TRUNCATED AT 250 WORDS)
Ledermann
S E
SE
Renal Unit, Hospital for Sick Children, London, UK.
Johnson
A
A
Dillon
M J
MJ
Trompeter
R S
RS
Barratt
T M
TM
D000293:Adolescent; D002118:Calcium / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D015592:Immunoradiometric Assay; D007223:Infant; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000150:complications; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*
D010281:Parathyroid Hormone; D003404:Creatinine; D002118:Calcium