Humoral Hypercalcemia of Malignancy Factor; Parathyroid Related Polypeptide; Parathyroid Related Protein; PRP; PTH Related Peptide; PTHRP, Plasma; PTH Related Protein; Parathyroid Hormone Related Peptide
Test ID
PTHRP
General Information
Useful for:
As an aid in the evaluation of patients with hypercalcemia of unknown origin
As an aid in the evaluation of patients with suspected humoral hypercalcemia of malignancy
The test should not be used to exclude cancer or screen tumor patients for humoral hypercalcemia of malignancy.
Specimen Type
EDTA Plasma
Specimen Requirements
Ice-cooled, lavender top (EDTA)
Specimen Collection / Processing Instructions
Centrifuge specimen in a refrigerated centrifuge or in chilled centrifuge cups
Aliquot plasma into plastic vial and freeze
Minimum Sample Volume
0.25 mL
Stability
Frozen: 30 days
Unacceptable Specimen Conditions
Gross hemolysis
Limitations
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 cannot 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
