PTH-Related Protein
| Label Mnemonic: | PTHRP |
| Epic code: | LAB8205 |
| Downtime form: | A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery |
Commercial Mailout Laboratory
6240-8 RCP
356-8593
6240-8 RCP
356-8593
Specimen(s):
Plasma
Specimen
Instructions:
Collect sample in pre-chilled 3 mL lavender
EDTA tube.
Collection Medium:
 |
| Lavender top tube 3 mL (EDTA) |
Minimum:
Preferred Minimum: 0.7 mL
Absolute Minimum: 0.25 mL
Absolute Minimum: 0.25 mL
Turn Around
Time:
2 days upon receipt at reference laboratory
Reference Range:
<2.0 pmol/L
Interpretive Data:
Depending on the patient population, up to 80% of patients with
malignant tumors and hypercalcemia will be suffering from humoral
hypercalcemia of malignancy (HHM). Of these, 50% to 70% might have an
elevated parathyroid hormone-related peptide (PTHrP) level. These
patients will also usually show typical biochemical changes of excess
parathyroid hormone (PTH)-receptor activation, namely, besides the
hypercalcemia, the might have hypophosphatemia, hypercalcuria,
hyperphosphaturia and elevated serum alkaline phosphatase. Their PTH
levels will typically be less than 30 pg/mL or undetectable.
In patients with biochemical findings that suggest but do not prove primary hyperparathyroidism (eg, hypercalcemia, but normal or near normal serum phosphate and a PTH level that is within the population reference range, but above 30 pg/mL), HMM should be considered as a diagnostic possibility, particularly if the patient is elderly, has a history of malignancy or risk factors for malignancy. An elevated PTHrP level in such a patient is highly suggestive of HHM as the cause for the hypercalcemia.
In patients with biochemical findings that suggest but do not prove primary hyperparathyroidism (eg, hypercalcemia, but normal or near normal serum phosphate and a PTH level that is within the population reference range, but above 30 pg/mL), HMM should be considered as a diagnostic possibility, particularly if the patient is elderly, has a history of malignancy or risk factors for malignancy. An elevated PTHrP level in such a patient is highly suggestive of HHM as the cause for the hypercalcemia.
Comments:
Useful For:
• Diagnostic work-up of patients with suspected hypercalcemia of malignancy
• Diagnostic work-up of patients with hypercalcemia of unknown origin
Cautions:
The test should not be used to exclude cancer or screen tumor patients for humoral hypercalcemia of malignancy.
Parathyroid hormone-related peptide (PTHrP) can be elevated in pregnant and lactating women and in newborn infants. Nonmalignant conditions that have been described in association with elevated plasma PTHrP levels include systemic lupus erythematosus, HIV- associated lymphadenopathy, lymphedema of chest or pleural cavities, and with benign tumors of the ovary, kidney and the neuroendocrine system.
Because of the complexity of PTHrP isoforms, the differences between various PTHrP assays and the lack of a common calibration standard, PTHrP measurements performed with different assays can not be compared easily.
The complex isoform mixture of PTHrP can occasionally lead to pronounced nonlinearity on dilution of patient specimens. In these situations an accurate measurement of PTHrP concentrations might be impossible.
Like all immunometric assays, PTHrP assays are susceptible to false low results at extremely high analyte concentrations ("hooking") and to rare false positive results due to heterophile antibody interference. Therefore, if test results are incongruent with the clinical picture, the laboratory should be contacted.
• Diagnostic work-up of patients with suspected hypercalcemia of malignancy
• Diagnostic work-up of patients with hypercalcemia of unknown origin
Cautions:
The test should not be used to exclude cancer or screen tumor patients for humoral hypercalcemia of malignancy.
Parathyroid hormone-related peptide (PTHrP) can be elevated in pregnant and lactating women and in newborn infants. Nonmalignant conditions that have been described in association with elevated plasma PTHrP levels include systemic lupus erythematosus, HIV- associated lymphadenopathy, lymphedema of chest or pleural cavities, and with benign tumors of the ovary, kidney and the neuroendocrine system.
Because of the complexity of PTHrP isoforms, the differences between various PTHrP assays and the lack of a common calibration standard, PTHrP measurements performed with different assays can not be compared easily.
The complex isoform mixture of PTHrP can occasionally lead to pronounced nonlinearity on dilution of patient specimens. In these situations an accurate measurement of PTHrP concentrations might be impossible.
Like all immunometric assays, PTHrP assays are susceptible to false low results at extremely high analyte concentrations ("hooking") and to rare false positive results due to heterophile antibody interference. Therefore, if test results are incongruent with the clinical picture, the laboratory should be contacted.
Methodology:
Immunochemiluminometric Assay (ICMA)
CPT Code:
82397
See Additional Information:
Specimens Requiring Immediate Delivery
Specimens Requiring Immediate Delivery