Pathology Handbook

MPO & PR3 antibodies

Clinical Indications

Autoimmune vasculitides including:
Wegener's granulomatosis
Microscopic polyangiitis
Crescentic glomerulonephritis
Churg-Strauss syndrome
Please note: All samples found to be ANCA IIF positive or to have an interfering ANA will be tested for the presence of MPO and PR3 antibodies. 
The assay should not be considered diagnostic and a definitive diagnosis should not be based on the results of this assay alone

Test Includes

Detection of IgG autoantibodies against myeloperoxidase and proteinase 3

Request Form 

Request via ICE


Assay performed daily; Monday to Friday.

Specific Criteria

It is essential to provide relevant clinical information.
It is essential to inform laboratory by telephone of any urgent requests

Turnaround Time

All tests are performed on the next routine working day after receipt of the sample.




7 ml


Red top tube
Vacutainer red top


Samples should be transported to the laboratory immediately

Lab Handling

Aliquot and store at 4-8°C prior to testing and at -20°C or below for up to 1 month after receipt.

Causes for Rejection

Unlabelled/inadequately labelled sample
Inadequately completed request form
Delay in sample reaching laboratory

Reference Range

Negative: MPO <3.5 IU/mlPR3 <2 IU/ml

Equivocal: MPO 3.5-5.0 IU/ml PR3 2-3 IU/ml

Positive: MPO >5.0 IU/mlPR3 >3 IU/ml