Understanding Lab Tests for Granulomatosis with Polyangiitis
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
Granulomatosis with Polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a rare autoimmune condition that causes inflammation of blood vessels (vasculitis). This systemic disease can affect multiple organs including the lungs, kidneys, and upper respiratory tract. Specific blood tests are essential for diagnosing this condition.
Recommended Test
Inflammatory Bowel Disease Differentiation Panel
This comprehensive panel includes testing for both MPO (myeloperoxidase) antibodies and Proteinase-3 antibodies, which are key diagnostic markers for Granulomatosis with Polyangiitis. Proteinase-3 antibodies are commonly found in GPA patients and serve as a primary diagnostic biomarker. MPO antibodies, while more common in Microscopic Polyangiitis, can also be detected in some GPA cases. This panel provides essential antibody testing needed to support the diagnosis of this rare vasculitis condition.
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How Blood Tests Diagnose Granulomatosis with Polyangiitis
The diagnosis of GPA relies heavily on detecting specific autoantibodies in the blood called ANCA (Anti-Neutrophil Cytoplasmic Antibodies). These antibodies target proteins within white blood cells and serve as important diagnostic biomarkers. The presence of these antibodies, combined with clinical symptoms and sometimes tissue biopsy, helps confirm the diagnosis.
Understanding Your Results
Positive results for Proteinase-3 antibodies strongly suggest GPA, while MPO antibodies may be present in some cases. However, antibody levels can vary, and some patients may have negative results despite having the disease. Your healthcare provider will interpret these results alongside your symptoms and may recommend additional testing or imaging studies to confirm the diagnosis.
Important Considerations
The information here is for educational purposes only and is not a substitute for professional medical advice. Granulomatosis with Polyangiitis requires specialized medical care and treatment. Always consult with a healthcare provider or rheumatologist for proper diagnosis and treatment.
