Tests and diagnosisBy Mayo Clinic staff
A diagnosis is fairly easy to make when the classic rash, joint pain and gastrointestinal symptoms are present. If only one or two are present, diagnosis can be more of a challenge.
Although no single laboratory test can confirm Henoch-Schonlein purpura, certain tests can help rule out other diseases and make a diagnosis of Henoch-Schonlein seem likely.
In addition to conducting a physical exam and taking a medical history, your doctor may request several tests, including:
- Blood tests. An elevated level of a special type of protein called IgA may suggest Henoch-Schonlein purpura, but it isn't conclusive. Another indication may be an elevated erythrocyte sedimentation rate — commonly referred to as sed rate. By measuring how quickly red blood cells fall to the bottom of a tube of blood in an hour, this test may indicate the level of inflammation in the body.
- Urine tests. These evaluate kidney function to determine whether the disease is affecting the kidneys. It can take several months after the appearance of the rash for the kidneys to be affected, so your doctor may want to repeat the urine tests monthly for up to six months. Blood in the urine, as well as elevated levels of certain proteins, can help your doctor determine the extent to which the kidneys are affected by the disease.
- Skin biopsy. If there are doubts about the rash or if other tests are inconclusive, your doctor may take a small sample of skin to be sent to a lab and examined under a microscope for the presence of IgA in the blood vessels.
- Kidney biopsy. A kidney biopsy is a more invasive procedure, but your doctor may request it if there are signs and symptoms of severe kidney involvement, such as high blood pressure or sudden onset of kidney failure, especially if the tests above are not conclusive. Results of the kidney biopsy can help your doctor decide on appropriate treatment.
- Imaging studies. Your doctor may request an abdominal ultrasound to rule out other causes of abdominal pain, such as appendicitis or a tear in the bowel (perforation), or to check for possible complications, such as bowel obstruction.
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