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Test Code Parathryroid Hormone (PTH), Intact Parathyroid Hormone (PTH), Intact

Important Note

Use the single order Parathyroid Hormone (PTH), Intact for all PTH testing needs, including intraoperative cases. Laboratory notification of scheduled parathyroidectomies is required.

Additional Codes

Cerner

NextGen

Parathryroid Hormone (PTH), Intact

PTH Intact

Alternate Name(s)

iPTH

Intact PTH

Parathormone

Parathyrin

Useful For

Parathyroid hormone (PTH) is secreted by the parathyroid gland; after being secreted into the bloodstream, it undergoes extensive proteolysis to generate various fragments. In contrast to its degradation products, the concentration of Intact PTH is relatively independent of glomerular filtration rate and reflects the biologically active portion of the hormone.

The primary role of PTH is to maintain calcium homeostasis via its interaction with calcitonin. PTH measurement is an important aid in the diagnosis of disorders of calcium metabolism. PTH synthesis and secretion are triggered rapidly by low concentrations of ionized calcium. The biological activities of PTH are to increase absorption of dietary calcium, decrease renal clearance and mobilize skeletal calcium stores. Abnormally high ionized calcium concentrations suppress secretion of PTH.  In conjunction with serum calcium levels, the PTH assay may be used as an aid in the differential diagnosis of hypercalcemia, hypocalcemia and parathyroid disorders. PTH determination is important in monitoring dialysis patients to manage renal osteodystrophy.

Intraoperative PTH testing is used during surgery for hyperparathyroidism, especially in minimally invasive or directed procedures, as well as for patients undergoing reoperation. For patients undergoing parathyroidectomy it is recommended that preoperative and pre-excision samples are taken.  Samples should also be drawn at 5 and 10 minutes post resection and a >50% reduction in PTH levels from the highest baseline may be used as criteria for surgical success.

Methodology

Immunometric Immunoassay

Patient Preparation

None

Collection Instructions

  • Standard phlebotomy practices.
  • Plasma should be thoroughly separated from cellular material within 45 minutes of collection.
  • Specimen types should not be used interchangeable during the serial monitoring of an individual patient as measured concentrations may vary slightly between sample types.

Specimen Requirements

Container

Specimen Type

Tube

Lithium Heparin Plasma

Must be separated within 45 minutes.

PST

Must be separated within 45 minutes.

 or 

 

Stability

Storage

Temperature

Stability

Room Temperature

15-30°C

Up to 8 hours

Refrigerated

 2-8°C

Up to 48 hours

Frozen

≤-20 °C

Do not freeze specimens

Rejection Criteria
  • Gross Hemolysis
  • Turbid Specimens
  • Specimens that have been frozen

Result Reporting and Reference Values

Reported in pg/mL

Intraoperative sample drawn 5-10 minutes post-excision should decrease by at least 50% from the baseline sample.

Age

Low

High

Birth -18 Years

Not Defined

18-150 Years

14.2

75.2

Reflex Testing

None

Limitations

  • Ortho reports a bias with the following:
    • Patients taking Cefoxitin Sodium could have reported PTH concentrations that are negatively biased at levels indicated in the Known Interferences section.
    • Rheumatoid factor at concentrations of 450 IU/mL and above have been shown to falsely elevate PTH test results.
    • Total protein at concentrations of 11.6 g/dL and above have been shown to falsely decrease PTH test results. 
  • Ortho reports no significant effect with the following:
    • Bilirubin up to 40 mg/dL
    • Rheumatoid factor concentrations less than 225 IU/mL have demonstrated no observed interference.
    • Total protein at concentrations less than 9.4 g/dL have demonstrated no observed interference.