Systemic Lupus Erythematosus Diagnosis and Evaluation

Essential blood tests and antibody checks for Lupus.

Clinical Immunology focuses on the immune system’s health. Learn about the diagnosis and treatment of allergies, autoimmune diseases, and immunodeficiencies.

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Systemic Lupus Erythematosus: Diagnosis and Tests

Diagnosing Systemic Lupus Erythematosus is a complex clinical puzzle. There is no single test that provides a simple yes or no answer. Instead, Liv Hospital specialists rely on a combination of clinical observations, patient history, and a battery of sophisticated laboratory tests. Rheumatologists typically use classification criteria, such as those established by the EULAR or ACR, to help guide diagnosis. These criteria weigh various clinical and immunological features to determine if a patient falls within the lupus spectrum.

The Antinuclear Antibody Test

The Gateway Test

The Antinuclear Antibody or ANA test is the primary screening tool for lupus. It detects antibodies that target the nucleus of the body’s cells.

Sensitivity: ANA is positive in more than 98 percent of patients with systemic lupus. A negative ANA test makes lupus extremely unlikely.
Specificity: However, a positive ANA is not specific to lupus. It can be seen in other autoimmune diseases, viral infections, and even in healthy individuals. Therefore, a positive result requires further detailed testing to determine the specific type of antibody present.

Specific Autoantibody Profiles

Anti dsDNA

Antibodies to double-stranded DNA are highly specific for SLE. They are rarely found in people who do not have lupus. Furthermore, the levels of Anti dsDNA often fluctuate with disease activity. A rising titer can predict an impending flare, particularly involving the kidneys.

Anti Smith

Antibodies to the Smith nuclear antigen are also highly specific for lupus. While they are less sensitive and found in only about 30 percent of patients, their presence is virtually diagnostic for the disease. Unlike anti-dsDNA, anti-Smith levels tend to remain stable and do not correlate with disease flares.

Anti Ro and Anti La

These antibodies are found in lupus but also in Sjögren syndrome. Their presence is important for counseling women of childbearing age, as they are associated with a risk of neonatal lupus and congenital heart block in the fetus. They are also associated with photosensitive skin rashes.

Complement Levels

Measuring Immune Consumption

The complement system is a group of proteins that work with the immune system to clear pathogens. In active lupus, immune complexes form and consume these complement proteins.

C3 and C4: Low levels of Complement C3 and C4 in the blood indicate that the immune system is actively fighting and consuming these resources. This is often a sign of active kidney disease or systemic vasculitis. Monitoring these levels helps physicians gauge how active the disease is at any given moment.

Assessment of Organ Involvement

Urinalysis and Biopsy

Given the risk of silent kidney damage, urine tests are mandatory.

Urinalysis: Checks for protein (proteinuria), red blood cells (hematuria), and cellular casts.
Kidney Biopsy: If kidney involvement is suspected, a biopsy is the gold standard. It involves taking a small sample of kidney tissue to examine under a microscope. This determines the class of lupus nephritis (ranging from Class I to Class VI), which dictates the aggressiveness of the required treatment.

Complete Blood Count

A CBC is performed to detect hematological issues.

Leukopenia: Low white blood cell count.
Thrombocytopenia: Low platelet count.
Hemolytic Anemia: Identified by low red blood cells and markers of cell destruction, such as elevated reticulocytes.

Inflammatory Markers

ESR and CRP

Erythrocyte Sedimentation Rate and C-Reactive Protein are general markers of inflammation. In lupus, the ESR is frequently elevated during flares. Interestingly, the CRP may remain normal or only slightly elevated unless there is serositis (inflammation of the lung or heart lining) or a bacterial infection. A very high CRP in a lupus patient often prompts a search for an infection rather than just attributing it to the lupus itself.

Imaging Modalities

Evaluating Systemic Damage

Chest X-ray and CT Scan: Used to detect fluid around the lungs (pleural effusion) or interstitial lung disease.
Echocardiogram: An ultrasound of the heart used to check for fluid around the heart (pericardial effusion), valve abnormalities, or pulmonary hypertension.
MRI: Utilized to evaluate the brain in patients with neurological symptoms to rule out strokes or inflammation of the brain tissue.
Joint Ultrasound: Can detect synovitis (inflammation of the joint lining) even when it is not obvious on physical examination.

The Antiphospholipid Panel

Clotting Risk Assessment

Since blood clots are a major risk, testing for antiphospholipid antibodies is routine.

Lupus Anticoagulant: A misnomer, as it promotes clotting in the body despite prolonging clotting times in the test tube.
Anticardiolipin Antibodies: Associated with arterial and venous thrombosis.
Anti Beta 2 Glycoprotein I: Another marker for clotting risk.
Positivity in these tests usually requires long-term blood-thinning therapy if a clot has occurred.