Diagnosis of lupus can be problematic. Making a correct diagnosis of lupus requires knowledge and awareness on the part of the doctor and good communication on the part of the patient.
An accurate medical history, physical examination and the results of laboratory tests help the doctor consider other diseases that may mimic lupus or determine if you truly have the disease.10
The most useful tests to aid a diagnosis identify certain autoantibodies often present in the blood of people with lupus. For example, the antinuclear antibody (ANA) test is commonly used to look for autoantibodies that react against components of the nucleus of the body's cells.
About 98% of people with lupus possess ANA, which can attack the nucleic material of your cells. However, there are a number of other causes of a positive ANA besides lupus, including infections and other autoimmune diseases.
Diagnostic tools for lupus include:
In people with a positive ANA, more tests are usually performed to check for other antibodies that can help confirm a diagnosis.
Certain autoantibodies and substances in the blood can give information about which autoimmune disease, if any, is present. To check for other antibodies, doctors usually order an ANA panel, which checks for the following antibodies:17
1) Antiphospholipid antibodies (APLs)
APLs are a type of antibody directed against phospholipids. APLs are present in up to 60% of people with lupus.
A positive test is also used to help identify women with lupus that have certain risks that require preventive treatment and monitoring. Those risks include blood clots, miscarriage, or preterm birth.
2) Anti-double-stranded DNA antibody
The anti-double-stranded DNA antibody (anti-dsDNA) is a specific type of ANA antibody found in about 30% of people with lupus. The presence of anti-dsDNA antibodies often suggests a more serious form of lupus, such as lupus nephritis (kidney lupus).
3) Anti-Smith antibody
An antibody to Sm, a ribonucleoprotein found in the nucleus of a cell, is found 20% of people with lupus. Unlike anti-dsDNA, anti-Sm does not correlate with the presence of kidney lupus.
4) Anti-U1RNP antibody
Anti-U1RNP antibodies are commonly found along with anti-Sm antibodies in people with lupus. The incidence of anti-U1RNP antibodies in people with lupus is approximately 25%. Anti-U1RNP has been shown to be associated with features of scleroderma, including Raynaud's phenomenon. It has also been linked to other conditions, such as Jaccoud's arthropathy, a deformity of the hand caused by arthritis.
5) Anti-Ro/SSA and anti-La/SSB antibodies
Anti-Ro/SSA and anti-La/SSB are antibodies found mostly in people with lupus (30-40%) and primary Sjögren's syndrome. They are also commonly found in people with lupus who have tested negative for ANA.
Babies of mothers with anti-Ro and anti-La antibodies are at an increased risk of neonatal lupus, an uncommon condition that produces a temporary rash and can lead to congenital heart block. Therefore, women with lupus who wish to become pregnant should be tested for these antibodies.
6) Anti-histone antibodies
Antibodies to histones, proteins that help to lend structure to DNA, are usually found in people with drug-induced lupus, but they can also be found in people with SLE. However, they are not specific enough to lupus to be used to make a concrete diagnosis.
A serum complement test measures the levels of proteins consumed during the inflammatory process. Low complement levels reflect that inflammation is taking place within the body. Variations in complement levels exist in different individuals simply due to genetic factors.
Some laboratories also include other antibodies in their panel, including antinucleoprotein or anticentromere.
Besides blood tests used to diagnose and monitor lupus, doctors use urine tests to diagnose and monitor the effects of lupus on the kidneys. These tests include the following:19
Other laboratory tests are used to monitor the progress of the disease after diagnosis, and the effectiveness of medications include:18
X-rays and other imaging tests can help doctors see the organs affected by lupus.
A rheumatologist's diagnosis is considered the gold standard, with the American College of Rheumatology (ACR) using a standard classification scheme that requires 4 of 11 criteria for research definition. This system can sometimes fail to recognize or miss early and mild cases.
The 11 criteria for the diagnosis of lupus include:3,14
There is frequent underdiagnosis of lupus due to the symptoms and signs not being specific. Equally, there is frequent overdiagnosis of the condition because doctors use a positive blood test (present in 5% of the healthy population) by itself to make a diagnosis.
On the next page we look at the treatment options for lupus and some of the measures that patients can take to cope with the disease.
Disclaimer: This informational section on Medical News Today is regularly reviewed and updated, and provided for general information purposes only. The materials contained within this guide do not constitute medical or pharmaceutical advice, which should be sought from qualified medical and pharmaceutical advisers.
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