It can take a few steps to find out whether you have Churg-Strauss syndrome. This rare disease is hard to diagnose based on its typical symptoms like fever, asthma, appetite loss, and tiredness. The trouble is that many conditions can cause these same symptoms.
There also isn't a single test to diagnose Churg-Strauss syndrome. Your doctor will look at many different things, including your symptoms, a physical exam, and the results of your lab and imaging tests.
The process will start with an exam. Your doctor will ask about your symptoms, and whether you've had asthma in the past. Asthma is common in people with Churg-Strauss syndrome.
6 Criteria for Diagnosis
The American College of Rheumatology has set up six "criteria" -- or standards -- for diagnosing Churg-Strauss syndrome. These are signs that most people with the condition have.
Your doctor will diagnose you with Churg-Strauss syndrome if you meet four of these six criteria:
Asthma. Most people with Churg-Strauss syndrome have this breathing problem. But just because you have asthma doesn't mean you definitely have this condition. Only a small number of people with asthma have it.
High level of eosinophils. These white blood cells help your body fight infections. Normally, 1% to 3% of your white blood cells are made up of eosinophils. Inflammation from Churg-Strauss syndrome can cause your eosinophil count to rise until these cells make up more than 10% of your total white blood cells.
Nerve damage. Inflammation from Churg-Strauss syndrome can damage nerves in your hands and feet. This leads to symptoms like numbness, pain, and burning.
Lesions. Eosinophils can get into your lungs and cause damage that shows up as spots on a chest X-ray. These may look similar to the spots on the lung X-rays of people with pneumonia.
Sinus problems. People with Churg-Strauss syndrome often have swelling in their sinuses, called sinusitis.
Eosinophils outside of your blood vessels. Testing a piece of tissue from your skin or nose may show that you have these particular white blood cells outside of your blood vessels.
Diagnostic Tests
Doctors diagnose Churg-Strauss syndrome using one or more of these tests:
Blood tests. Your doctor may order them to measure the number of eosinophils in your blood, or to check for signs of inflammation in your body. High eosinophil levels can mean that you have Churg-Strauss syndrome or asthma.
In Churg-Strauss syndrome, your immune system -- your body's defense against germs -- makes proteins called autoantibodies that attack your own tissues. A blood test called ANCA looks for these autoantibodies.
Only about 30% to 50% of people with Churg-Strauss syndrome will have a positive ANCA test, so it alone can't confirm the diagnosis.
Urine tests. People with Churg-Strauss syndrome may have too much protein or too many red blood cells in their urine. These can be signs of kidney damage.
Imaging tests. An X-ray or CT scan looks for damage in the lungs or checks for growths called polyps in the sinuses.
Biopsy. If other tests suggest that you might have Churg-Strauss syndrome, your doctor will confirm the results with a biopsy. The doctor removes a small piece of tissue from your lungs, skin, or other organs. Then a lab checks the sample under a microscope for signs of inflammation or damage.
Biopsy results in people with Churg-Strauss syndrome often show:
- High numbers of eosinophils
- Clusters of immune cells called a granuloma
- Blood vessel damage caused by immune cells, called vasculitis
Lung function tests. Your doctor may do a test called spirometry to check your breathing. If you have trouble breathing out, it could mean that you have asthma.
Bronchoscopic lavage. A bronchoscope is a thin, flexible tube with a camera on one end that helps your doctor see inside your airways. During this test, the doctor can rinse part of your lung with fluid, and then remove the fluid to test for eosinophils and other signs of Churg-Strauss syndrome.
Heart tests. Churg-Strauss syndrome can sometimes damage the heart. Your doctor might do an electrocardiogram (EKG) to check your heart's electrical signal, or an echocardiogram to see how well it pumps.