Blood Tests For Lupus
A healthy body creates antibodies to fight infections like bacteria, viruses and fungi. In people with lupus, these antibodies mistake healthy tissue as an invader, causing inflammation that damages those tissues.
Unlike many other diseases, no one blood test result means that you have lupus. Instead, your doctor will look at several tests, your medical history, and current symptoms to diagnose you and measure the severity of your disease. Blood tests are used to track the levels of several kinds of antibodies and proteins often found in the body of someone with lupus. This helps your doctor understand how much inflammation is taking place in your body.
The most common blood tests used to test for lupus include:1-3
- Complete blood count
- Blood chemistry panel
- Comprehensive metabolic panel
- Immunologic tests
- Positive antinuclear antibody (ANA)
- AVISE® CTD to confirm a positive ANA test
Complete blood count
A complete blood count, or CBC, which measures red blood cells, white blood cells, and platelets. An abnormal CBC is common in people with lupus. The CBC may show that you have:1-3
- High white cell count, which means you have an infection or are taking steroids.
- Low white blood cell count (leukopenia), which can be caused by lupus, a virus, or certain drugs.
- Low platelet count (thrombocytopenia), which means that the bone marrow is not making enough platelets or that antibodies are attacking your platelets.
- Low red blood cell count can indicate you have anemia, a vitamin deficiency, or bleeding. About 40 percent of people with lupus become anemic at some point
Inflammation of the heart, blood vessels, lungs and kidneys can impact how well your body functions in many ways. A comprehensive metabolic panel measures the level of sugar (glucose), minerals, proteins, electrolytes, and fluid balance in the blood. This gives your doctor an indication of kidney and liver function, and how well your metabolism is working.1-3
Antinuclear antibody (ANA)
Ninety-seven percent of people with lupus test positive for antinuclear antibodies. However, the ANA test alone is not enough to diagnose lupus. Between 5 percent and 10 percent of healthy people test positive for ANA, and 20 percent of healthy women will have a weak positive ANA test. People with other types of connective tissue diseases such as scleroderma and rheumatoid arthritis might also have a positive ANA test. This is why your doctor will look at other test results, any current symptoms and medical history to diagnose lupus.1-3
If you test positive for ANA, your doctor may order a more sensitive blood test called the AVISE® CTD, and an ANA panel, which checks for specific antibodies: anti-double-stranded DNA, anti-Smith, anti-U1RNP, anti-Ro/SSA, anti-La/SSB, anti-nucleoprotein, anticentromere, or antihistone.
Your doctor will only test your ANA once. After you have been diagnosed with lupus, your levels of anti-double-stranded DNA (anti-dsDNA) will be checked at every visit to monitor your disease.
If you test positive for ANA, your doctor may order the AVISE CTD, a blood test that can confirm lupus and other autoimmune diseases such as rheumatoid arthritis, Sjogren’s syndrome, or scleroderma. The AVISE test measures the lupus biomarkers called cell-bound complement activation products (CB-CAPs).1-3
Less than one percent of healthy people produce anti-double-stranded DNA (anti-dsDNA) but 30 percent of people with lupus do. The presence of anti-dsDNA antibodies suggests more serious lupus, especially lupus nephritis (kidney lupus). The tests used to detect anti-dsDNA include the enzyme-linked immunosorbent assay (ELISA), the Crithidia luciliae immunofluorescence test, and radioimmunoassay.2
The anti-Sm antibody is found in 20 percent of people with lupus, but rarely in healthy people or those with other rheumatic diseases. This means anti-Sm can help eliminate other diseases that mimic lupus. Tests to measure anti-Sm include ELISA, counter immunoelectrophoresis (CIE), immunodiffusion, or hemagglutination.2
Anti-U1RNP antibodies are found in one percent of healthy people but about 25 percent of people with lupus. Anti-U1RNP antibodies are not specific to lupus. These antibodies are also found in people with other rheumatic conditions, such as rheumatoid arthritis, systemic sclerosis, Sjogren’s syndrome, and polymyositis.2
Anti-Ro/SSA and anti-La/SSB antibodies
Anti-Ro/SSA and anti-La/SSB antibodies are found 30 percent to 40 percent of people with lupus and Sjogren’s syndrome. People with lupus who have tested negative for anti-nuclear antibodies often test positive for anti-Ro/SSA and anti-La/SSB antibodies. Only about 15 percent of healthy people produce these antibodies. These antibodies are associated with extreme sun sensitivity and a sub-type of lupus called subacute cutaneous lupus erythematosus (SCLE).1-3
Anti-histone antibodies are most often found in people with drug-induced lupus but people with systemic lupus erythematosus sometimes produce these antibodies.1-3
Complements are a group of proteins that help regulate the body’s immune response. A blood complement test measures the levels of these proteins, so a low blood complement level means inflammation is taking place in the body.1-3
Antiphospholipid antibodies appear in the blood of about 50 percent of people with lupus. The number of antibodies found in a person with lupus may increase and decrease over time.1-3
The antiphospholipid antibodies most often found are the lupus anticoagulant (LA) and anticardiolipin antibody (aCL). They can be found together or alone. Other antibodies that may be found include anti-beta 2 glycoprotein 1 (anti-ß2 GPI), anti-prothrombin, and the “false-positive” test for syphilis.
People with these antibodies are more likely to experience miscarriage, antiphospholipid Antibody Syndrome (APS) and blood clots, which may cause stroke, heart attack and other serious complications. People without lupus can also have antiphospholipid antibodies.1-3
Other blood tests
Depending on your symptoms, your doctor may also order C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR or sed rate) tests. High CRP levels in the blood suggest liver inflammation. ESR measures a protein that makes red blood cells clump together, making it test for both inflammation and infection.1-3