Calcium-corrected intact PTH: a clinically useful parameter for quantifying parathyroid function in patients undergoing hemodialysis.
OBJECTIVE
Serum parathyroid hormone (PTH) concentration provides a rough index of the severity of secondary hyperparathyroidism (SHPT) due to chronic renal failure. Since serum PTH inversely related to calcium (Ca) level, we attempted to create a new index based on the relationship.


METHODS
Our subjects were 70 patients undergoing maintenance hemodialysis (HD) in a single facility. Using multiple pairs of serum Ca corrected for albumin (cCa) and intact PTH (iPTH) values drawn simultaneously, we determined the steepest slope of cCa-iPTH relationship for each individual patient to get a line closely resembling the cCa-PTH sigmoidal curve.


RESULTS
Based on the slopes, the following equation was obtained: iPTH2 = iPTH1 + (cCa1 - cCa2) x (43 + 0.47 x iPTH1), where the PTH values at any 2 arbitrary values of cCa1 and cCa2 were assumed to be iPTH1 and iPTH2, respectively. When 'corrected PTH' is defined as the predicted value of iPTH at cCa = 9.0 mg/dl, its correlation was better than iPTH with the total volume of the parathyroid glands estimated by ultrasonography. Similar results were found in 30 parathyroidectomized patients at other facilities.


CONCLUSIONS
'Corrected PTH' may represent a useful parameter for assessing the severity of SHPT from single determinations of cCa and iPTH drawn at the same time.
Yano
Shozo
S
Department of Internal Medicine 1, Shimane University Faculty of Medicine, Shimane, Japan. syano@med.shimane-u.ac.jp
Brown
Edward M
EM
Takase
Hirofumi
H
Wada
Akihiko
A
Suzuki
Keiko
K
Kobayashi
Akira
A
Sugimoto
Toshitsugu
T
D000368:Aged; D015415:Biomarkers / Q000097:blood; D002118:Calcium / Q000097:blood*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000175:diagnosis* / Q000209:etiology*; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*; D006435:Renal Dialysis / Q000009:adverse effects*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D015415:Biomarkers; D010281:Parathyroid Hormone; D002118:Calcium