Test Details
Methodology
Plasma: electrochemiluminescence immunoassay (ECLIA); serum: colorimetric
Result Turnaround Time
Within 1 day
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Use
This test is used for differential diagnosis of hypercalcemia. PTH is an 84-amino acid peptide hormone that is responsible for the regulation of serum calcium levels within a narrow range.
PTH is secreted in response to decrease in serum calcium levels by increasing the renal reabsorption of calcium and lowering reabsorption of phosphorus. The measurement of PTH is a useful tool in the differential diagnosis and management of hypercalcemia. PTH assays can be of help in the diagnosis of tumors and hyperplasia of the parathyroid gland, as well as in localizing hyperfunctioning parathyroid tissue by assay of samples obtained via venous catheterization. The native or intact (1-84) PTH has a short half-life, measured in minutes, whereas the carboxy and midmolecule fragments, which are biologically inactive, have half-lives 10- to 20-fold higher. The high concentrations of biologically inactive fragments have interfered with use of C-terminal or midmolecule assays for evaluation of parathyroid function in patients with impaired renal function. Intact PTH assays provide a more accurate assessment of parathyroid patients including those with various renal diseases.
Special Instructions
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
References
Specimen Requirements
Specimen
Plasma and serum
Volume
1.5 mL plasma and 1 mL serum
Minimum Volume
0.7 mL plasma and 0.5 mL serum
Container
Lavender-top (EDTA) tube and red-top tube or gel-barrier tube
Collection Instructions
Transfer separated plasma to a plastic transport tube clearly labeled as EDTA plasma and maintain refrigerated temperature. If red-top tube is used, transfer serum to a plastic transport tube clearly labeled as serum.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | Serum: 14 days |
Plasma: 2 days (stability determined by manufacturer or literature reference) | |
Refrigerated | Serum: 14 days |
Plasma: 3 days (stability determined by manufacturer or literature reference) | |
Frozen | Serum: 14 days |
Plasma: 6 months (stability determined by manufacturer or literature reference) | |
Freeze/thaw cycles | Serum: Stable x3 |
Plasma: Stable x1 (stability determined by manufacturer or literature reference) |
Storage Instructions
Serum: Room temperature
Plasma: Refrigerated
Causes for Rejection
Whole blood; plasma other than EDTA; hemolysis; room temperature serum sent for PTH intact
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 054601 | Ca+PTH Intact | 24346-9 | 001016 | Calcium | mg/dL | 17861-6 |
| 054601 | Ca+PTH Intact | 24346-9 | 015610 | PTH, Intact | pg/mL | 2731-8 |
| 054601 | Ca+PTH Intact | 24346-9 | 004000 | Intact PTH | N/A | |
| Order Code | 054601 | |||||
| Order Code Name | Ca+PTH Intact | |||||
| Order Loinc | 24346-9 | |||||
| Result Code | 001016 | |||||
| Result Code Name | Calcium | |||||
| UofM | mg/dL | |||||
| Result LOINC | 17861-6 | |||||
| Order Code | 054601 | |||||
| Order Code Name | Ca+PTH Intact | |||||
| Order Loinc | 24346-9 | |||||
| Result Code | 015610 | |||||
| Result Code Name | PTH, Intact | |||||
| UofM | pg/mL | |||||
| Result LOINC | 2731-8 | |||||
| Order Code | 054601 | |||||
| Order Code Name | Ca+PTH Intact | |||||
| Order Loinc | 24346-9 | |||||
| Result Code | 004000 | |||||
| Result Code Name | Intact PTH | |||||
| UofM | ||||||
| Result LOINC | N/A |