Systemic lupus erythematosus (SLE) can be a difficult condition to diagnose. This is because symptoms of SLE are sometimes similar to several other conditions, most of which are far more common than SLE.
Diagnosis may also be difficult because symptoms can vary greatly from person to person. They may also change over time. For example, there may be periods where your symptoms are not very noticeable, or times when they flare up and become more severe.
If your GP suspects SLE after examining your symptoms, they will refer you for blood tests to help confirm the diagnosis.
Some blood tests that may be carried out are listed below.
Anti-nuclear antibody test
An anti-nuclear antibody test checks whether there is a certain type of antibody cell in your blood, known as the anti-nuclear antibody. Approximately 95% of people with SLE have this antibody.
However, it is possible to have the anti-nuclear antibody without having SLE, so the anti-nuclear antibody test is not a definitive way of testing for the condition. Your GP will need other tests to confirm the diagnosis.
Anti-DNA antibody test
An anti-DNA test also checks for a certain type of antibody in your blood. If you have the anti-DNA antibody, it is highly likely you will have SLE. However, the antibody can also be present in people who do not have the condition.
The level of anti-DNA antibodies increases when SLE is more active, so during a flare-up of symptoms your reading from this test may be greater than normal.
Complement level test
Complement is a chemical in the blood that forms part of your immune system. Your GP may test the level of this chemical in your blood to check how active your SLE is. The level of complement in your blood decreases when SLE is more active.
Once you have been diagnosed with SLE, you will normally need regular monitoring to see how the condition is affecting your body.
If you have SLE it is possible you may develop other conditions, such as anaemia or kidney problems. Monitoring your condition will allow your doctor to check for these secondary conditions and, if necessary, treat them as soon as possible.
You may need to have a scan, such as an X-ray, ultrasound scan or a computerised tomography (CT) scan to check whether SLE is affecting your internal organs.