Lupus (SLE) is a persistent, inflammatory autoimmune disorder affecting many organ systems, including the blood cells, internal organs, joints and skin, especially kidneys and, in some cases, the brain.
Lupus affects more women than men, usually between 20 – 40 years old. However, it also affects children, newborns and older adults. People of Asian and African descent have a higher risk of lupus.
The cause of lupus is still unknown but may involve a genetic factor and a trigger related to hormones or environmental factors. Some medications may also cause lupus, and this condition may occur alongside other autoimmune disorders such as the antiphospholipid syndrome and sjögren’s syndrome.
Identifying the symptoms of lupus is the first step in its diagnosis. The symptoms of lupus vary between people. Many of these symptoms are similar to those of arthritis and diabetes. Sometimes, the symptoms flare up and go away for no known reason.
These reasons make diagnosing lupus difficult. However, a few symptoms seem common with lupus. They include rashes or a rash, usually butterfly rash, that covers the joins at the bridge of the nose and cheeks. The rashes may also affect the wrists, hands and other parts of your face. They are usually itchy and occur after long exposure to the sun. Some rashes clear within a short time, and others remain for long.
Other common symptoms of lupus are:
If you notice these symptoms, ensure you consult your healthcare professional. Your medical professional will examine you and ask about the details of the symptoms. Consider keeping track of your symptoms over time to give your doctor the most accurate information.
The doctor will also ask about your family history to know if lupus runs in your family. If your doctor suspects lupus, they will recommend urine and blood tests for confirmation.
It is usually difficult to diagnose lupus because the symptoms and signs vary. The symptoms and signs usually change over time and are similar to several other conditions. There is no particular test to diagnose lupus, but urine and blood tests, a physical examination and the signs and symptoms may help the doctor make an accurate diagnosis.
The urine and blood tests for lupus may include:
CBC measures the number of blood cells, such as the white blood cells, red blood cells, platelets and haemoglobin (a protein in the red blood cells). The result of this test may indicate anaemia, which is common in lupus. Lupus may also cause a low blood platelet or white blood cell count.
This blood test helps determine how long red blood cells take to move to the bottom of a tube in one hour. A faster than normal sedimentation rate may indicate systemic disease like lupus.
The sedimentation rate isn’t specific for any disease but may be elevated if you have an infection, cancer, lupus or another inflammatory condition.
Different blood tests can assess the liver and kidney function. These tests are important because lupus can affect the liver and kidneys.
Examining the urine sample may show elevated erythrocytes or protein levels in your urine, which may occur when lupus affects the kidneys.
When the immune system is stimulated, it produces ANA, which results in a positive ANA test. A positive ANA test may occur for people with lupus, but some people with a positive ANA test result do not have lupus. Your doctor may recommend a more specific antibody test if you have a positive ANA test result.
If your doctor suspects you have lupus and it affects your heart or lungs, they may suggest:
Chest x-ray – Chest imaging may show abnormal shadows that suggest lung inflammation or fluids in the lungs.
Echocardiogram – An echocardiogram uses sound waves to show real-time images of the heart beating. It checks for problems in the heart’s valves and other parts of the heart.
Lupus can affect the kidneys differently, so treatment will vary depending on the damage. Sometimes, testing a small kidney tissue sample may be necessary to determine the best treatment. This sample can be obtained using a needle or through a small incision.
A skin biopsy may also be necessary to confirm a diagnosis of lupus that affects the skin.
What is it? – ANA is an antibody directed against the nucleus of the cells.
What is the test for? – Most people with active lupus have ANA. Doctors recommend this test as a screening tool for lupus. Checking the antibody’s pattern may help the doctor determine the specific disease, which helps determine the most effective treatment.
Limitations of this test – Although most people with lupus have ANA, a positive result doesn’t always indicate lupus. People with some other diseases may have positive results, and a small percentage of the antibody is present in people without lupus and other autoimmune disorders.
A positive ANA result alone isn’t enough to diagnose lupus. Doctors will consider the result alongside other factors.
What is it? – APLs are an antibody directed against phospholipids
What is the test for? – About 60% of people with lupus have APLs. The presence of these antibodies can confirm lupus diagnosis. A positive APL test can also help diagnose women with lupus who have certain risks requiring monitoring and preventive treatment. These risks include preterm birth, miscarriage and blood clots.
Limitations of the test – APLs may be present in people who do not have lupus, so their presence alone isn’t sufficient to diagnose lupus.
What is it? – Anti-SM is an antibody for Sm, a specific protein present in the nucleus of cells.
What is the test for? – About 30% of people with lupus have Sm, but it is rare in people without lupus. A positive test can confirm a lupus diagnosis.
Limitations of the test – The anti-Sm test is positive in up to 30% of people with lupus, so only this test can miss most cases of lupus.
What is it? – Anti-dsDNA is a protein directed against the double-stranded DNA. DNA contains the body’s genetic code.
What is the test used for? – The anti-dsDNA test is positive in about 75% – 90% of people with lupus. This test is also specific for lupus, so a positive result will confirm a diagnosis.
For most people with lupus, the antibody level increases as the disease becomes more active. This allows doctors to measure the activity of the disease. A positive anti-dsDNA test indicates a higher risk of kidney inflammation with lupus (lupus nephritis), so a positive result can alert the doctor to monitor the kidneys.
Limitations of this test – About 25% of people with lupus have a negative result, so a negative result doesn’t always mean the absence of lupus.
What is it? – Anti-La (SSB) and Anti-Ro (SSB) are usually found together. These antibodies are specific against RNA (ribonucleic acid) proteins.
What is the test for? – 35% of Sjögren’s syndrome patients have Anti-La, about 24% – 60% of people with lupus have Anti-RO and 70% of people with Sjögren’s syndrome, an autoimmune.
The presence of these antibodies helps in diagnosing lupus and Sjögren’s syndrome. The antibodies are also associated with neonatal lupus, a rare but life-threatening problem affecting newborns.
A positive Anti-La (SSB) and Anti-Ro (SSB) in pregnant women can warn the doctor to monitor the unborn baby.
Limitations of this test – Like other antibody tests, many people with lupus do not have a positive result. This test is more likely to diagnose Sjögren’s syndrome than lupus.
What is it? – CRP is a common inflammation marker in the body.
What is the test for? – This test checks for inflammation, which may indicate active lupus. Sometimes, the test helps monitor inflammation, and results may show changes in response to treatment or disease activity.
Limitations of the test – An elevated CRP has several causes, including infection, so the test doesn’t confirm a lupus diagnosis and cannot distinguish an infection from a lupus flare. The level of CRP doesn’t indicate the activity of lupus disease, so it isn’t useful in monitoring the disease activity.
What is it? – Complement protein is an inflammation marker. This test can check the levels of specific protein or total complement protein.
What is the test for? – Complement protein levels are usually low in patients with active disease, particularly kidney disease, so healthcare professionals can use the test to monitor or determine disease activity.
Limitations of the test – Interpretation of complement test must be in the contest of other test results and clinical findings. A low complement result alone cannot diagnose lupus.
What is it? – ESR is a common blood test that measures the rate at which red blood cells move towards the bottom of a test tube. Inflammation in the body causes blood proteins to stick together and fall faster as sediment. The faster blood cells fall, the higher the severity of the inflammation.
What is the test for? – ESR is an inflammation marker, as inflammation may indicate lupus activity. This test helps monitor inflammation, indicating a response to treatment or disease activity.
Limitations of the test – The ESR test isn’t specific to lupus, like the CRP test. A positive result may occur for different reasons, including infection, so the test isn’t diagnostic for lupus. This test cannot also differentiate an infection from a lupus flare, and the level doesn’t directly indicate lupus disease activity, meaning it cannot monitor the disease activity.
What is it? – The CBC test measures the levels of different blood cells.
What is the test for? – Abnormal blood cell count, including red and white blood cells, may occur in lupus patients. This may be due to an infection, lupus or lupus treatment. For example, about 50% of lupus patients have leukopenia, a condition with decreased white blood cell count.
About 50% of people with lupus also have thrombocytopenia (low platelet count). Doctors may recommend this test to monitor these potentially life-threatening problems.
Limitations of the test – Several medical conditions can cause abnormal blood cell counts, so only this test cannot diagnose lupus.
What is it? – This test assesses liver or kidney function. It also provides information on blood sugar, triglyceride, cholesterol and electrolyte levels.
What is the test for? – Abnormalities in this test may indicate complications from lupus, including the treatment effect for these complications like liver disease, increased cholesterol levels, kidney disease and increased blood sugar levels.
What is it? – It measures the kidney’s effectiveness in filtering the blood to remove waste products. The glomerular filtration rate calculation includes age, gender, creatinine levels and race (but the calculation with race is phasing out). It checks the stage of kidney disease.
Doctors also use urine tests to diagnose lupus and monitor its effect on the kidneys. These urine tests include:
The urine protein test measures the amount of albumin, a protein, in your urine. Even a small amount of albumin in the urine indicates a risk for kidney disease.
This test measures how well the kidneys filter waste products from blood. It is done on urine collected over a 24-hour timeframe.
Urinalysis screens for kidney disease. The presence of red blood cells, cellular casts, proteins and white blood cells in the urine may indicate kidney disease.
We offer different lupus blood tests at Blood London, including other tests for the disease. Visit Blood London today for your lupus blood test, or call us on 020 71830244 to book an appointment for your test.
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