Comparison of intact and 'whole molecule' parathyroid hormone assays in patients with histologically confirmed post-renal transplant osteodystrophy.
BACKGROUND
Fragments of parathyroid hormone (PTH) have been identified (amino acids 7-84) which may interfere with commercially available 'intact molecule' PTH assays. Novel assays which employ an antibody directed to the first seven amino acids of the N-terminus of PTH are thought to be free from cross-reactivity with the 7-84 fragments, and therefore measure true 'whole molecule' PTH. Transplant recipients (as well as those in end-stage renal failure) have been reported to have elevated levels of 'intact' in comparison with 'whole molecule' PTH.


METHODS
PTH concentrations were assessed in serum samples obtained from female renal transplant recipients previously classified as either having hyperparathyroid (n = 14) or adynamic bone disease (n = 14) by transiliac crest bone biopsy. PTH was measured as 'whole molecule' (Scantibodies 'whole molecule' PTH) and 'intact' (DPC Immulite 2000 intact PTH and Scantibodies total PTH).


RESULTS
Scantibodies 'whole molecule' PTH (all-subject mean 48.7 ng/L, +/- 53.0) were significantly lower than DPC intact (83.5 ng/L, +/- 88.1; P < or = 0.0001) and Scantibodies total PTH (80.5 ng/L, +/- 92.4; P < or = 0.0001). However, the differences between the 'whole molecule' and 'intact' measurements were similar across the two patient groups, and reflected the lower reference range employed by the 'whole molecule' assay.


CONCLUSIONS
The 'whole molecule' PTH assay was unable to discriminate between the two patient populations and provided very little additional clinical information to that obtained from the intact PTH assays.
Godber
Ian M
IM
Department of Clinical Chemistry, Nottingham City Hospital, UK. igodber@ncht.trent.nhs.uk
Parker
Cornelle R
CR
Lawson
Nigel
N
Hitch
Tony
T
Porter
Christine J
CJ
Roe
Simon D
SD
Cassidy
Michael J D
MJ
Hosking
David J
DJ
D000918:Antibody Specificity; D016477:Artifacts; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D016030:Kidney Transplantation; D010281:Parathyroid Hormone / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D012680:Sensitivity and Specificity
D010281:Parathyroid Hormone; D010446:Peptide Fragments