How is lupus diagnosed?
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Your doctor will make the diagnosis based on the history of your illness, a physical examination and blood tests. Test results help to distinguish lupus from other conditions that may have similar symptoms.
A number of different blood tests may be used:
- Anti-nuclear antibody (ANA) test
About 95% of people with lupus are ANA positive, but the test can sometimes be positive in people without lupus so it can’t confirm the diagnosis.
- Anti-double-stranded DNA (anti-dsDNA) antibody test
About 70% of people with lupus have these antibodies. A positive test means that it’s highly likely that you have lupus. The level usually goes up when lupus is more active, so repeat tests may be helpful in monitoring your condition and when deciding on treatment.
- Anti-Ro antibody test
If you test positive for this autoantibody you may be more likely to get skin rashes and to suffer from Sjögren’s syndrome. It can pass across the placenta in pregnancy. If you carry it and decide to have a baby, your pregnancy will be more closely monitored.
- Antiphospholipid antibody test
A positive test for these autoantibodies may mean an increased risk of miscarriage and developing blood clots.
- Complement level test
Complement refers to a set of proteins in the blood that protect us from infections. Levels go down when lupus is more active.
- Erythrocyte sedimentation rate (ESR) test
This measures inflammation. The ESR is often raised in lupus.
- Kidney and liver function tests
These include blood and urine tests. They’re carried out regularly so that any problems caused by lupus itself or by the treatments you’re using can be recognised and dealt with quickly.
- Blood cell counts
Haemoglobin, white and red blood cells and platelets are all made in the bone marrow, so blood cell counts can help to show whether the bone marrow is affected by your condition or the drugs you’re using to treat it.
These tests can also be helpful in monitoring your condition after diagnosis and may, for example, be helpful in predicting a flare-up of the disease or deciding whether you have an infection.
A variety of tests are available to check how your heart, lungs, liver and spleen are working. Depending on which organs your doctor thinks may be involved, you may have x-rays, an ultrasound scan, a computerised tomography (CT) scan or a magnetic resonance imaging (MRI) scan.
A urine test can show if there’s protein or blood in the urine. This can help doctors to recognise a problem in your kidneys at a very early stage. You may need further tests, such as kidney filtration tests.
If you have fever, weight loss or swelling of the lymph glands, your doctor may take a biopsy of lymph gland tissue to rule out cancer, which can also cause these symptoms.
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