Which laboratory test is most likely to be ordered to evaluate systemic lupus erythematosus?

The most appropriate laboratory test for evaluating systemic lupus erythematosus (SLE) is the measurement of anti-dsDNA antibody levels. This specific antibody is highly associated with SLE and is often used as a marker for disease activity. Elevated levels of anti-dsDNA are indicative of active lupus and can correlate with disease flares, particularly around kidney involvement, which is a significant complication of the disease.

In contrast, other tests are less specific for SLE. Creatinine kinase levels primarily assess muscle damage and are not specific for autoimmune disorders like lupus. C-reactive protein levels can indicate inflammation but do not specifically correlate with SLE activity; they might be elevated in a variety of inflammatory conditions. Thyroid function tests evaluate the thyroid gland and are unrelated to the diagnosis and management of SLE.

Thus, the focus on anti-dsDNA antibodies uniquely positions this test as a key element in the diagnosis and monitoring of lupus, making it the most appropriate choice in this scenario.