Plain, EDTA and heparin tubes are accepted, with or without gel separator.
Stability of PTH in plain, EDTA or heparin tubes (less than 10% change):
Unseparated : Serum - centrifuged immediately due to instability. Plasma - up to 6h at room temperature
Separated : Serum sample stability - 8 hr at 15-25 o C , 2 days at 2-8 o C, 6 months and -20 o C
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Intraoperative PTH assays must be arranged with the Section Head of Automation, LabPlus (ext 22118, or contact via LabLink ext 22000) at least one day before the operation. The turnaround time is approximately 35 minutes from receipt of the sample. Hand deliver samples to ensure no transport delays. |
Plasma Sample stability:
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2 days at 15-25 o C
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3 days at 2-8 o C
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6 months at -20 o C
Units: pmol/L
Reference range: 1.7 - 7.3
Uncertainty of Measurement: 0.6pmol/L at level of 3 pmol/L
10% at levels of 10 pmol/L or higher
Conversion factor : ng/L x 0.106 = pmol/L
Principle: Sandwich type immunoassay with chemiluminescence detection
Reagents: Roche PTH
Analyser: Cobas e801
Hypercalcemia with raised or normal PTH : primary or tertiary hyperparathyroidism
Hypercalcemia with low PTH : Hyprcalcemia of malignancy (PTHrP-mediated), myeloma, sarcoidosis, vitamin D overdosage, milk-alkali syndrome
Hypocalcemia with raised PTH : Renal failure, Vitamin D or calcium deficiency (rickets, osteomalacia), pseudohypoparathyroidism (PTH resistance)
Hypocalcemia with low or normal PTH : hypoparathyroidism
References
Stokes, F. J., P. Ivanov, et al. (2011). "The effects of sampling procedures and storage conditions on short-term stability of blood-based biochemical markers of bone metabolism." Clin Chem 57 (1): 138-140.
Parathyroid hormone in other fluids
Turnaround time :
Within 1 week
Important note:
This test is not routinely available at LabPLUS. Please contact the chemical pathologist prior to collection of the sample (usually a prearranged ultrasound-guided procedure). Urgent testing, e.g. during parathyroid surgery, is not available.
The method for measuring PTH at LabPlus is also not formally validated in saline and LabPlus cannot provide reference intervals. Individual results should be considered cautiously, taking into account the clinical context and the results of other investigations.
Diagnostic use and interpretation :
In selected cases, a fine needle aspiration (FNA) may be performed to determine if a mass represents parathyroid tissue. A specialist may request parathyroid hormone (PTH) testing in saline used to wash the needle. There is limited good quality evidence available, but PTH testing sometimes appears to be a useful but imperfect addition to cytology.
Specimen collection :
Collection processes vary widely in the literature. We recommend:
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Washing the FNA needle with saline only
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Clearly indicating on the test form the number of needles used, volume of saline used
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Clearly indicate the site of collection of each specimen (if more than one specimen)
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Indicate the name of the chemical pathologist that accepted the request
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Record time and date of collection
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If the sample will arrive at LabPLUS within 4 hours of collection, transport promptly at room temperature. if >4hrs, send frozen
Stability :
LabPLUS has not formally investigated the stability of PTH in saline, however it has been reported to be around 4 hours by Mayo Clinic. Prompt delivery to the lab is required for best results.
See also:
Entry on cytology
Entry on aspirated fluids
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427