A 44-year-old female with a malar rash and renal damage is suspected to have SLE. What initial test should be recommended for screening?

In the diagnosis of systemic lupus erythematosus (SLE), the initial screening test of choice is the anti-nuclear antibodies (ANA) test. This test is critical because ANA is present in a majority of SLE cases, making it a useful preliminary indicator of the disease. Although a positive ANA test is not specific to SLE and can be found in other autoimmune conditions and even in healthy individuals, it is a necessary step in the diagnostic process for SLE.

Following a positive ANA result, further specific antibody tests, such as anti-Smith (Anti-Sm) antibodies and antihistone antibodies, can help confirm the diagnosis of SLE and differentiate it from other conditions. In contrast, rheumatoid factor is more related to rheumatoid arthritis and does not play a central role in diagnosing SLE. Therefore, beginning with the ANA test allows clinicians to efficiently assess the likelihood of SLE given the patient's symptoms.