Comparison of two immunoradiometric assays for parathyroid hormone-related protein in the evaluation of cancer patients with and without hypercalcemia

Miguel, Fernando de; Motellón, J.L; Hurtado, Jesús; Jiménez, F. Javier; Esbrit, Pedro

doi:10.1016/s0009-8981(98)00127-2

Cited by 15 publications

(11 citation statements)

References 16 publications

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“…The interindividual variation in the reduction of PTHrP concentrations in samples analyzed fresh and after storage could be related to the differences in concentrations of endogenous proteases causing PTHrP degradation. Similar observations have been reported in earlier publications (11,12 ). In agreement with our data, the PTHrP degradation rate varied among the samples from different individuals.…”

Section: Discussionsupporting

confidence: 93%

“…On the basis of our data, increased concentrations of PTHrP in samples of patients with suspected hypercalcemia are more common than was stated previously. Our observation on poor agreement between the methods for PTHrP is not unique; poor agreement between the commercial RIAs was described in other studies (11,12 ).…”

Section: Discussionsupporting

confidence: 76%

“…PTHrP is known to be very unstable (11,12 ). In samples of 4 of the 5 individuals, PTHrP concentrations in samples collected in PPACK tubes were higher than in the other 5 evaluated types of tubes (mean difference, 30%).…”

Section: Resultsmentioning

confidence: 95%

“…PTHrP in plasma samples is unstable and undergoes rapid degradation (11,12 ). Of the evaluated types of blood collection tubes, PTHrP concentrations were highest in the tubes with PPACK inhibitor (analyzed immediately after defrosting).…”

Section: Discussionmentioning

confidence: 99%

“…This observation could be related to the poor performance of available PTHrP assays, which underestimate PTHrP concentrations, resulting in a very low positivity rate in samples from patients clinically suspected of hypercalcemia. Because of the poor performance, previously available methods were not able to reliably measure PTHrP in healthy individuals (11)(12)(13)(14), resulting in the assumption that PTHrP is not present in circulating blood in health. In this study, we identified a large number of patient samples with substantial disagreement in results between the commercial RIA and our LC-MS/MS assay (Fig.…”

Section: Discussionmentioning

confidence: 99%

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LC-MS/MS Measurement of Parathyroid Hormone–Related Peptide

et al. 2016

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INTRODUCTION Parathyroid hormone–related peptide (PTHrP) is involved in activating pathways, allowing tumor cells to form bone metastases. Measurement of PTHrP is used for the diagnosis and clinical management of patients suspected of hypercalcemia of malignancy. We developed an LC-MS/MS method for measuring PTHrP, established sex-specific reference intervals, and assessed the method's performance. METHODS PTHrP was enriched from plasma samples with rabbit polyclonal anti-PTHrP antibody conjugated to magnetic beads. Enriched PTHrP was digested with trypsin, and PTHrP-specific tryptic peptide was analyzed with 2-dimensional LC-MS/MS in multiple reaction monitoring mode. RESULTS The lower limit of quantification was 0.6 pmol/L, and the upper limit of linearity was 600 pmol/L. Total imprecision was <10%. Very poor agreement was observed with the RIA (n = 207; Deming regression RIA = 0.059 × LC-MS/MS − 1.8, r = 0.483; Sy|x = 3.9). Evaluation of the clinical performance of the assay using samples from patients with and without hypercalcemia (n = 199) resulted in an area under the ROC curve of 0.874. In sets of consecutively analyzed routine samples of patients assessed for hypercalcemia, the PTHrP positivity rate by RIA (n = 1376) was 1.9%, and 26.6% by LC-MS/MS (n = 1705). Concentrations were below the lower limit of quantification in 95.6% of the samples by RIA and 2.0% by LC-MS/MS. CONCLUSIONS PTHrP is a normal constituent in circulating blood and its concentrations are substantially underestimated by commercial RIAs, causing false-negative results in samples from patients suspected of hypercalcemia. Our observations suggest a link between increased concentrations of PTHrP in postmenopausal women with low body mass index and increased incidence of osteoporosis.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 76%

Section: Resultsmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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LC-MS/MS Measurement of Parathyroid Hormone–Related Peptide

et al. 2016

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High Sensitivity Measurement of Parathyroid Hormone–Related Protein (PTHrP) in Plasma by LC-MS/MS

Kushnir

Rockwood

2022

Clinical Applications of Mass Spectrometry in Biomolecular Analysis

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Age-Related Changes in Parathyroid Hormone-Related Protein and Vascular Endothelial Growth Factor in Human Osteoblastic Cells

Martínez

Esbrit²,

Rodrigo

et al. 2002

Osteoporosis International

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Osteogenesis and angiogenesis occur in a coordinated manner in skeletal tissue, so that impaired angiogenesis is associated with decreased bone formation in aged subjects. However, the interaction between bone endothelium and osteoblastic cells is poorly understood. Parathyroid hormone-related protein (PTHrP), a bone factor which modulates osteoblastic cell growth and/or differentiation, stimulates vascular endothelial growth factor (VEGF), a potent angiogenic factor, in primary cultures of human osteoblastic (hOB) cells. In the present study, we examined the age-related changes of both factors in these cells. Human OB cells were isolated from trabecular bone samples from knee or hip explants obtained from 45 osteoarthritic patients: 12 <60 years (21-59 years), 5 women and 7 men, and 33 >60 years (61-82 years), 20 women and 13 men. Cell total RNA was isolated, and mRNA analysis was performed by reverse transcription-polymerase chain reaction. Relative ratios of amplified products with respect to glyceraldehyde-3-phosphate dehydrogenase were then calculated. PTHrP and VEGF were measured in the cell-conditioned medium, after stimulation with (or without) 10 nM 1,25(OH)(2)D(3) for 72 h, using specific immunoradiometric assay and a competitive immunoassay, respectively. A positive correlation was found between PTHrP and VEGF (both mRNA and secreted protein), and also between PTHrP mRNA and the secreted protein levels, in these cells. PTHrP, both mRNA and protein secretion levels, and VEGF secreted values were higher in knee hOB cells than in hip hOB cells only in the younger group. In addition, a decrease in the secreted levels of these factors occurs with aging only in hOB cells from knee. Treatment with 10 nM 1,25(OH)(2)D(3) induced a lower inhibitory response of PTHrP secretion, and a higher stimulatory response of secreted VEGF, in hOB cells with age. These findings indicate that age-related bone loss in humans is associated with a decrease in the osteoblastic secretion of both PTHrP and VEGF in the knee, a predominantly trabecular bone. These data might provide a rationale to explain the impaired angiogenesis associated with trabecular bone loss in aging.

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Comparison of two immunoradiometric assays for parathyroid hormone-related protein in the evaluation of cancer patients with and without hypercalcemia

Cited by 15 publications

References 16 publications

LC-MS/MS Measurement of Parathyroid Hormone–Related Peptide

LC-MS/MS Measurement of Parathyroid Hormone–Related Peptide

High Sensitivity Measurement of Parathyroid Hormone–Related Protein (PTHrP) in Plasma by LC-MS/MS

Age-Related Changes in Parathyroid Hormone-Related Protein and Vascular Endothelial Growth Factor in Human Osteoblastic Cells

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