Performance and diagnostic application of a two-site immunoradiometric assay for parathyrin in serum.
The "N-tact" immunoradiometric assay (IRMA) from INCSTAR for parathyrin (PTH) in serum involves a 125I-labeled affinity-purified antiserum to PTH 1-34 and an affinity-purified antiserum to PTH 39-84, the latter bound to a polystyrene bead. The mean detection limit, determined in six consecutive assays, was 4 ng/L. The within-batch CV was less than 7% in the range 15 to 2135 ng/L. The between-batch CV was 11.7% and 5.3% at 30 and 371 ng/L, respectively. Serum PTH in 14 proven cases of primary hyperparathyroidism was 49-808 (median 111) ng/L, undetectable (less than 5 ng/L) in 10 cases of primary hypoparathyroidism and in 10 cases of hypercalcemia associated with malignancy, compared with 7-39 ng/L in 45 normal subjects. PTH was 9 to 19 ng/L in four patients with familial benign hypercalcemia. In 39 patients with renal failure, apparent concentrations were 14 to 857 (median 133) ng/L, but sera from these patients pre-diluted with zero standard did not parallel dilutions of the standard, PTH 1-84. PTH concentrations were not significantly decreased in blood or serum kept at 20 degrees C for up to 6 h. After successful removal of a parathyroid adenoma, the mean half-time for disappearance of PTH in vivo in five hyperparathyroid patients was 3.3 min.
Wolfson Research Laboratories, Department of Clinical Chemistry, Queen Elizabeth Medical Centre, Birmingham, U.K.
W A
WA
Ratcliffe
D A
DA
Heath
M
M
Ryan
S R
SR
Jones
D000328:Adult; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000097:blood* / Q000209:etiology; D006961:Hyperparathyroidism / Q000097:blood / Q000175:diagnosis*; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood* / Q000493:pharmacokinetics; D010282:Parathyroid Neoplasms / Q000150:complications / Q000175:diagnosis*; D011863:Radioimmunoassay; D013048:Specimen Handling
D010281:Parathyroid Hormone