SLE can be difficult to diagnose. Symptoms can fluctuate and mimic those of other diseases. A doctor will make a diagnosis of SLE based on symptoms, medical history, physical exam and blood test for antinuclear antibodies. The doctor may also order other types of laboratory tests.
The American College of Rheumatology (ACR) has a classification system for helping doctors diagnose, or exclude, SLE. According to the ACR, at least four of the 11 criteria should be present for a diagnosis of lupus.
ACR Criteria for Diagnosing Systemic Lupus Erythematosus
1. Butterfly (malar) rash across cheeks and nose
2. Discoid (skin) rash, which appears as scaly raised red patches
4. Oral (mouth) ulcers
5. Arthritis in two or more joints; joints will have tenderness and swelling but will not have become deformed
6. Inflammation of the lining around the lungs (pleuritis) or the heart (endocarditis)
7. Evidence of kidney disease
8. Evidence of severe neurologic disease, such as seizures or psychosis
9. Blood disorders, including low red and white blood cell and platelet counts
10. Immunologic abnormalities as evidenced by positive tests for anti-double stranded DNA (anti-dsDNA), anti-SM, anti-Ro, and anti-LA antibodies
11. Positive antinuclear antibody (ANA) test
Note: A patient must experienced four of the criteria before a doctor can classify the condition as SLE. These criteria, proposed by the American College of Rheumatology, are not exclusive criteria for diagnosis, however.
Tests for Autoantibodies (ANA Test)
Antinuclear Antibodies (ANAs). A primary test for SLE checks for antinuclear antibodies (ANA), which attack the cell nucleus.
High levels of ANA are found in more than 98% of patients with SLE. Other conditions, however, also cause high levels of ANA, so a positive test is not a definite diagnosis for SLE:
- Antinuclear antibodies may be strongly present in other autoimmune diseases (such as scleroderma, Sjögren syndrome, or rheumatoid arthritis).
- They also may be weakly present in about 20 - 40% of healthy women.
- Some drugs can also produce positive antibody tests, including hydralazine, procainamide, isoniazid, and chlorpromazine.
A negative ANA test makes a diagnosis of SLE unlikely but not impossible. High or low concentrations of ANA also do not necessarily indicate the severity of the disease, since antibodies tend to come and go in patients with SLE.
Review Date: 02/18/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.