How is granulomatosis with polyangiitis (GPA) diagnosed?
GPA has symptoms similar to a number of other disorders, which may make it difficult to diagnose. However, for the most effective and successful treatment, early diagnosis is critical.
Once the diagnosis of GPA is suspected, a biopsy (tissue sample) of an affected area is often performed to try to confirm the presence of vasculitis. Biopsies are only recommended for organ sites in which there are abnormal findings present by examination, laboratory tests, or imaging.
It is the combination of symptoms, results of physical examinations, laboratory tests, X-rays, and sometimes a biopsy (sample) of affected tissue (skin, nasal membranes, sinus, lung, kidney or other sites) that together prove the diagnosis of GPA. Following treatment, these factors are also critical in judging whether the disease is active or in remission.
A positive blood test for antineutrophil cytoplasmic antibodies (ANCA) can support a suspected diagnosis of the disease. However, this blood test does not by itself prove the diagnosis of GPA or determine disease activity.
GPA often affects the lungs. In patients with GPA that have no lung symptoms (coughing or shortness of breath), imaging tests (conventional X-rays or a CT scan) will show lung abnormalities in up to one third of cases. Therefore, it is important to have lung images performed if active GPA is suspected, even if you do not have any symptoms of lung disease.