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PTD - 275

Test Directory - Parathyroid Hormone

Synonyms

PTH

Clinical Indications

Differential diagnosis of hypercalcaemia.
Assessment of parathyroid activity in patients with chronic renal failure.
Investigation and monitoring of patients with hyperparathyroidism secondary to vitamin D deficiency or malabsorption.
Investigation of hypocalcaemia.

Request Form

Combined Pathology Blood form (Yellow/Black)

Availability

On request, if specific criteria met.

Specific Criteria

Investigation of abnormal calcium status or monitoring renal bone disease.

Patient Preparation

Ideally, patients should be fasting (10 hours) except for renal patients. Calcium levels should be requested at same time.

Turnaround Time

Same day (Monday to Friday)

Specimen

Serum

Volume

2 ml

Container

Pink/purple top (EDTA) tube

Causes for Rejection

Unlabelled sample. Delay in sample reaching laboratory. Unnecessary repeat requesting.

Reference Range

1.6 - 6.9 pmol/L for normocalcaemic patients (Reference: Roche method insert)

However, most patients are being investigated for abnormal calcium levels and in non-parathyroid disease PTH levels should reflect calcium status (i.e. high calcium, low PTH). In the presence of hypercalcaemia, a clearly elevated PTH of >7.0 pmol/L is diagnostic of primary hyperparathyroidism, while an appropriately suppressed result of <2.6 pmol/L virtually excludes primary hyper-parathyroidism but could be due to Familial Benign Hypercalcaemia (FBH). Where the PTH is between 2.6 and 7.0 pmol/L, either primary hyperparathyroidism or FBH is possible and a fasting calcium excretion is indicated.

Interpretation

 

Critical Difference 72%

Unit Conversion

To convert from ng/L (pg/mL) to pmol/L multiply by 0.106

Lab Handling

 

Processing: Primary tube is given an 8 prefix barcode, it is then centrifuged and placed in the C311/E411 rack for analysis.


Version 1.0 / June 2014                                                                                                          Approved by: Consultant Biochemist