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PTD - 172

Test Directory -  Aquaporin Antibodies

Synonyms

Anti-Aquaporin-4 antibodies, NMO antibodies

Clinical Indications

Aquaporin 4 (AQP4) is a water channel protein found on cells known as astrocytes that surround the blood-brain barrier, (a layer of cells responsible for preventing dangerous substances in the blood from crossing into the brain). It is presumed that the blood brain barrier allows the AQP4 antibodies to enter the central nervous system. This causes an inflammation and demyelination and symptoms of a relapse. .

Investigation of suspected neuromyelitis optica (NMO). NMO is a severe inflammatory demyelinating disease that predominantly affects the optic nerve and spinal cord. Aquaporin-4 (AQP-4) antibodies have been identified as a specific serum marker for NMO. Approximately 80% of people diagnosed with NMO have Aquaporin 4 antibodies in their blood

The NMO spectrum of diseases in which AQP-4 antibodies are present include longitudinally extensive transverse myelitis (LETM), Sjögren's syndrome with myelopathy, and some patients with recurrent optic neuritis or SLE. Some of the NMO spectrum diseases can be confused with MS on initial presentation.

Request Form

A specific referral laboratory request form is preferred (please click here)

Availability

Referred test: Analysed by John Radcliffe Hospital, Oxford if specific criteria met.

Specific Criteria

Requested by Consultant Neurologist in the further investigation of suspected NMO spectrum diseases, usually with proven demyelinating disease.

Patient Preparation

None required

Turnaround Time

Two weeks

Specimen

Serum

Volume

2 ml

Container


Yellow top (SST) tube

paediatric orange top (lithium-heparin)

Causes for Rejection

Not meeting specific criteria

Interpretation

There are several (research) methods which may be used to detect AQP-4 antibodies and their sensitivity is approx. 90% with 100% specificity in a relapsing cohort of patients with NMO. These assays are more useful in helping to diagnose those patients who are likely to have relapsing NMO and Sjögren's syndrome with myelopathy . They are less often positive in patients with monophasic NMO.

Lab. Handling

Processing: Aliquot (MPA) and store at 4°C in separating fridge (CB39). Referral:  AQUAB and send or BPRO and save in separating freezer (CB40) at -20°C, saved frozen rack.

        

 


Version 1.0 / April 2014                                                                                                          Approved by: Consultant Biochemist