Plasma parathyroid hormone related-protein levels in patients with cancer, normocalcemic and hypercalcemic.

Hypercalcemia in patients with cancer may reflect the synthesis and secretion into circulation of parathyroid hormone-related protein (PTHrP) produced by the tumor. In the present study, we have measured circulating PTHrP concentrations in healthy subjects and patients using a new immunoradiometric assay (IRMA) that is specific for the 1-86 amino acid sequence of molecule, and in plasma collected with protease inhibitors. Plasma concentrations of PTHrP(1-86) were greater than the detection limit of the assay (0.3 pmol/l) in healthy subjects. All patients with hypercalcemia-associated cancer had PTHrP(1-86) levels significantly greater (median 7.74 pmol/l, P < 0.05) than healthy subjects or patients with cancer and normal serum calcium, primary hyperparathyroidism and hyperparathyroidism secondary to chronic renal failure. Plasma PTHrP and corrected serum calcium were correlated in patients with hypercalcemia-associated cancer. In one patient, a marked decrease in PTHrP and calcium levels was observed following surgery. Our results suggest that this IRMA for PTHrP(1-86) may be useful for diagnosis and monitoring of PTHrP-producing tumors induced hypercalcemia.

Automated quantification of TSH in serum by a chemiluminescent enzyme immunometric assay: analytical validation.

Thyroid stimulating hormone (thyrotropin; TSH) in serum was assayed with the Immulite-TSH, a fully automated solid-phase third-generation immunoassay analyzer that has a chemiluminescent detection system. The intraassay CV ranged from 3.6% to 6.2% for TSH mean concentrations from 0.025 to 32.12 mIU/L and the interassay CV ranged from 7.9% to 10% for TSH mean concentrations between 0.023 and 31.93 mIU/L. The analytical and functional detection limits of the assay were 0.001 and 0.0068 respectively. No interference was observed by any of the compounds: bilirubin, triglycerides, and hemoglobin. To compare the accuracy of Immulite-TSH with that of a conventional immuno-radiometric assay (Orion Diagnostica Irma-TSH), we examined 153 patient samples with TSH concentrations ranging approximately 0.2 to 100 mIU/L. At TSH concentration approximately 0.15 the precision was greater for Immulite-TSH than for Irma TSH (3.8% vs 11.87%) intraassay CV and (8.6% vs 35.4%) interassay CV. We concluded that Immulite-TSH is a rapid and precise third-generation assay, totally automated and the results can be provided to the clinician within 1 to 2 h of receipt of the patient's sample.