A 30-year-old woman with a 3-year history of systemic lupus erythematosus (SLE) presents to her rheumatologist for routine follow up. Her course has been complicated by lupus nephritis (baseline creatinine 1.1 mg/dL) and she has been on stable doses of methotrexate and hydroxychloroquine for the last 2 months following a flare. Which of the following lab values can be used to best monitor this patient’s disease?
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Anti-nuclear antibody
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Anti-dsDNA antibody
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Anti-Smith antibody
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Anti-RNP antibody
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CH50 level
View Explanation
In patients with SLE, the level of anti-dsDNA antibody can be used to monitor disease activity.
SLE is characterized by the production of auto-antibodies that, along with immune complex formation, cause the multi-organ manifestations of the disease. One such auto-antibody is anti-dsDNA. Anti-dsDNA has high specificity for SLE and is rarely found in the presence of other autoimmune conditions. There is an especially strong correlation between IgG anti-dsDNA and glomerulonephritis in the context of SLE. Serum C3 and C4 levels are also used to track SLE disease activity.
Illustration A is an algorithm for the laboratory diagnosis of lupus. Illustration B is a summary of the system-wide manifestations possible in lupus.
