PTH-Related Protein (Sendout)

General Information

Lab Name PTH_Related Protein Lab Code RPTHRP Epic Name PTH Related Protein (Sendout) External Test Id PTHRP Description

Useful For:

• Aiding in the evaluation of individuals with hypercalcemia of unknown origin
• Aiding in the evaluation of individuals with suspected humoral hypercalcemia of malignancy
• The test should not be used to exclude cancer or screen individuals with tumors for humoral hypercalcemia of malignancy

Synonyms Humoral Hypercalcemia of Malignancy Factor, Parathyroid Hormone-Related Peptide, Parathyroid Related Polypeptide, Parathyroid Related Protein, PRP, PTH Related Peptide, PTHrP Components

Interpretation

Method

Immunochemiluminometric Assay (ICMA)

Reference Range Units: pmol/L

Female	Male	Unknown
Age	Range	Age	Range	Age	Range
0-	0.0-4.2	0-	0.0-4.2	0-	0.0-4.2

Effective date: 04/30/2019

Ref. Range Notes

Interpretation:

Depending on the patient population, up to 80% of individuals 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, they 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), HHM should be considered as a diagnostic possibility, particularly if the patient is an older adult, has a history of malignancy, or has risk factors for malignancy. An elevated PTHrP level in such a patient is highly suggestive of HHM as the cause for the hypercalcemia.

Interferences and Limitations

Cautions:

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.

Ordering & Collection

Specimen Type Blood Collection

Collection:

• Prechill a 6 mL LAVENDER TOP (EDTA) tube.
• Draw blood from the patient into the pre-cooled tube, invert to mix, and immediately place on wet ice.
• Expedite transport to the laboratory.

Handling Instructions

Outside Laboratories:

• Keep sample on wet ice prior to centrifugation.
• Centrifuge sample in a refrigerated centrifuge.
  • If a refrigerated centrifuge is unavailable, chill the centrifuge carriers. Centrifuge specimen for 5 minutes or less, then promptly transfer plasma.
• Immediately transfer plasma to a separate plastic vial and freeze at -20°C. Transport on dry ice.

Stability: Frozen (required): 30 days; Refrigerated: Unacceptable; Ambient: Unacceptable.

Reject Due To: Unfrozen samples, gross hemolysis. Gross lipemia or gross icterus are acceptable.

Quantity Requested: 0.7 mL EDTA plasma
Minimum: 0.3 mL EDTA plasma

Processing

Receiving Instructions

Promptly centrifuge sample in a refrigerated centrifuge.* Immediately transfer plasma to a separate plastic vial and freeze at -20°C.

• *If a refrigerated centrifuge is unavailable, chill the centrifuge carriers. Centrifuge specimen for 5 minutes or less, then promptly transfer plasma.

Sendouts:

• Order Mayo Test: PTHRP.
• Interfaced: Yes [Interface: 601; Dept: MAFZ]

Stability: Frozen (required): 30 days; Refrigerated: Unacceptable; Ambient: Unacceptable.

Reject Due To: Unfrozen samples, gross hemolysis. Gross lipemia or gross icterus are acceptable.

Misc Sendout

Performance

Lab Department Sendouts Mayo Lab (FZ)(MAFZ) Frequency Performed: Monday through Thursday. Report Available: 2 to 5 days from sample receipt at Mayo. Available STAT? No Performing Location(s)

Sendout	Mayo Clinic Laboratories (Superior Drive) 800-533-1710 3050 Superior Drive NW Rochester, MN 55901

Billing & Coding

CPT Codes 82397 LOINC 15087-0 Interfaced Order Code UOW5009 Interfaced Result Code UOW5009