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Parathyroid Hormone

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

Test Codes

EPIC: LAB5815, Beaker: PTHG, Antrim #17229

Department

Chemistry

Instructions

NOTE: Total Calcium is included with a PTH order. If the patient also has an order for a chemistry panel that includes total calcium, then 2 calcium results will be reported on the patient’s chart.

Specimen Collection Criteria

INPATIENTS ONLY:

Collect: One Gold-top SST tube.

NOTE:  Add-On Testing is available only according to specimen stability.

Physician Office/Draw Specimen Preparation

OUTPATIENTS ONLY:

Collect one Gold-top SST tube. 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 refrigerate (2°– 8°C or 36°– 46°F) or freeze (-20°C/-4°F or below) immediately.

NOTE: Samples kept at Room Temperature for longer than 4 hours will not be accurate. Add-on testing is NOT available.

Preparation for Courier Transport

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

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

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 for inpatients only.
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

Laboratory

Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Troy Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory

Performed

Monday – Sunday.
Results available within two business days.

Reference Range

PTH: 8.0-72.0 pg/mL.

Test Methodology

PTH: Chemiluminescent Immunoassay.

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).

Contacts

Last Updated

2/27/2024