How is lupus diagnosed?

Since individuals with SLE can have a wide variety of symptoms and different combinations of organ involvement, no single test establishes the diagnosis of systemic lupus. To help doctors improve the accuracy of the diagnosis of SLE, 11 criteria were established by the American Rheumatism Association. These 11 criteria are closely related to the symptoms discussed above. Some people suspected of having SLE may never develop enough criteria for a definite diagnosis. Other people accumulate enough criteria only after months or years of observation. When a person has four or more of these criteria, the diagnosis of SLE is strongly suggested. Nevertheless, the diagnosis of SLE may be made in some settings in people with only a few of these classical criteria, and treatment may sometimes be instituted at this stage. Of these people with minimal criteria, some may later develop other criteria, but many never do.

The 11 criteria used for diagnosing systemic lupus erythematosus are

·         malar (over the cheeks of the face) "butterfly" rash,

·         discoid skin rash (patchy redness with hyperpigmentation and hypopigmentation that can cause scarring),

·         photosensitivity (skin rash in reaction to sunlight [ultraviolet light] exposure),

·         mucous membrane ulcers (spontaneous ulcers of the lining of the mouth, nose, or throat),

·         arthritis (two or more swollen, tender joints of the extremities),

·         pleuritis or pericarditis (inflammation of the lining tissue around the heart or lungs, usually associated with chest pain upon breathing or changes of body position),

·         kidney abnormalities (abnormal amounts of urine protein or clumps of cellular elements called casts detectable with a urinalysis),

·         brain irritation (manifested by seizures [convulsions] and/or psychosis),

·         blood-count abnormalities (low counts of white or red blood cells, or platelets, on routine blood testing),

·         immunologic disorder (abnormal immune tests include anti-DNA or anti-Sm [Smith] antibodies, falsely positive blood test for syphilis, anticardiolipin antibodies, lupus anticoagulant, or positive LE prep test),

·         and antinuclear antibody (positive ANA antibody testing [antinuclear antibodies in the blood]).

In addition to the 11 criteria, other tests can be helpful in evaluating people with SLE to determine the severity of organ involvement. These include routine testing of the blood to detect inflammation (for example, tests called the sedimentation rate and C-reactive protein), blood-chemistry testing, direct analysis of internal body fluids, and tissue biopsies. Abnormalities in body fluids and tissue samples (kidney, skin, and nerve biopsies) can further support the diagnosis of SLE. The appropriate testing procedures are selected for the patient individually by the doctor.