Diabetes Insipidus, Arginine Vasopressin Neurophysin II: AVP Sequencing

Diagnostic Use

Familial neurohypophyseal diabetes insipisus (FNDI) is an uncommon, inherited disease with a uniform clinical phenotype characterised by persistent thirst, polydipsia, polyuria and a deficiency of the antidiuretic hormone, arginine vasopressin (AVP). The disease is transmitted in an autosomal dominant mode and appears to be largely, if not completely, penetrant. FNDI has been associated with degeneration of the magnocellular, neurohypophyseal neurons that normally synthesis AVP. Studies indicate that AVP secretion is normal for the first few days of life but then degenerates rapidly and may continue to decline slowly for a decade or more. Mutations appear to direct the production of a pre-prohormone that cannot be folded, processed or degraded properly, which gradually accumulates and eventually destroys vasopressinergic neurons.

Department

Genetics - Molecular Pathology

Delphic Registration Code

MOLP

Constituent Tests

• Genomic DNA Extraction

Synonyms

ADNDI
FNDI

Test Code

7312

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

4.0

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

1.0

Minimum Sample Volume (ml)

0.5

Additional Specimen Information

This test requires nucleated cells. Please do not centrifuge or freeze blood samples.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Aliquot Instructions

Sample Type

• Whole Blood

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Additional Referral/Aliquot Information

This test requires nucleated cells. Please do not centrifuge or freeze blood samples.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Test Method

Three coding exons of the AVP gene are amplified by PCR and analysed by automated bidirectional fluorescent DNA sequencing.

Non-Funded Test Cost

$949.14 (Exclusive of GST)

Billing Code

4566

Uncertainty of Measurement:
Automated bidirectional DNA sequencing has an analytical sensitivity and specificity of >99%. Note that the lower limit of variant detection of sequencing analysis is ~10%, this is important to consider in the case of mosaicism, mitochondrial, and somatic variation that is not expected to be present at 50% or 100%. This analysis will not detect variants located within intronic regions, except at the intron-exon boundaries.

Genomic DNA must be extracted from the specimen prior to testing. This incurs an additional charge (see GDNA). Laboratories may prefer to submit DNA for testing. Please provide a minimum of 5 micrograms of DNA at 20 nanograms/microlitre.

Contact Information

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