Lab Test

Parathyroid Hormone

Intact PTH, Intact Human Parathyroid Hormone, PTH, Whole Molecule

Test Codes

Antrim #17229, EPIC: LAB5815, SOFT: PTHG

Instructions

  • Because of the nocturnal rise in intact PTH levels, samples should be collected in the morning, after 7 am, preferably after an overnight fast.
  • Calcium is measured and reported with each PTH request.

Specimen Collection Criteria

Collect: Two Gold-top SST tubes.

  • One SST tube to be placed on ice for PTH testing and kept cold throughout the collection and separation process.
  • One SST tube is collected for calcium measurement.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Transfer serum for PTH measurement to a plastic transport tube and freeze (-20°C/-4°F or below) immediately. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube for calcium measurement within two hours of collection.

Preparation for Courier Transport

Transport: Serum for PTH measurement (Minimum: 2.0 mL), frozen (-20°C/-4°F or below), and centrifuged collection tube for calcium measurement (Minimum: 0.5 mL), refrigerated (2-8°C or 36-46°F).

Rejection Criteria

  • Samples that have not been collected and processed as indicated.
  • Lipemic, icteric, or hemolyzed specimens.
  • Specimens with gross bacterial contamination.

In-Lab Processing

Both tubes are placed on the Abbott input / output module for centrifugation and testing by the automated line instruments.

Storage

PTH Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 4 hours 
Refrigerated (2-8°C or 36-46°F): 2 days 
Frozen (-20°C/-4°F or below): 2 months
Frozen (-70°C/-94°F or below): 11 months

Calcium Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel

Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

PTH Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days, but cannot add on PTH after 48 hours.

Calcium Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Troy Chemistry Laborary
Royal Oak Special Testing & Automated Chemistry Laboratory

Performed

Monday – Sunday.
Results available within two business days.

Reference Range

PTH: 8-72 pg/mL.

Test Methodology

PTH: Chemiluminescent Immunoassay.
Calcium: Spectrophotometry.

Interpretation

PTH plays an important role in calcium homeostasis by maintaining the concentration of ionized calcium within the precise limits necessary to achieve metabolic and neuroregulatory functions of this essential mineral. At low levels of blood calcium, parathyroid glands increase secretion of the hormone. This results in mobilization of calcium from the large skeletal stores into the extra-cellular fluid, increased absorption of dietary calcium, and decreased renal clearance of urinary calcium. When blood calcium levels increase, smaller quantities of parathyroid hormone are secreted into the bloodstream.

Clinical Utility

The measurement of PTH is an important aid in the assessment of disorders of calcium metabolism. When evaluated along with calcium levels, the quantitation of PTH has proven useful in distinguishing normal individuals from patients with primary and secondary hyperparathyroidism and non-parathyroid hypercalcemia, including hypercalcemia of malignancy. The intact assay measures PTH amino acid sequence 1-84. N terminal (1-34) and carboxyl (C) terminal (35-84) peptide fragments do not interfere with the intact PTH assay. By eliminating cross reactivity with PTH Related Peptide, (similar peptide structure to N-terminal 1-13) this assay provides a more precise assessment of parathyroid function in patients with renal disease and in patients with age-related glomerular filtration diseases. Intact PTH values will be elevated in primary and secondary hyperparathyroidism, and suppressed in patients with hypercalcemia of malignancy.

CPT Codes

83970 (PTH), 82310 (Calcium).

Contacts

Last Updated

6/23/2020

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This directory currently reflects information only for specimens collected and/or processed at the
Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.