In diagnosing systemic lupus erythematosus (SLE), which laboratory test is considered useful?

The presence of antinuclear antibodies (ANA) is a key indicator in diagnosing systemic lupus erythematosus (SLE). This test is crucial because SLE is characterized by the production of autoantibodies against nuclear components, leading to various systemic symptoms and organ involvement. A positive ANA test suggests an autoimmune process is occurring, which is central to the diagnosis of SLE, especially when it is correlated with clinical findings such as rash, joint pain, and other systemic manifestations.

Testing for ANA is commonly one of the first tests performed when SLE is suspected. While a positive test is not exclusive to SLE—since it can be positive in other autoimmune disorders—it is an essential part of the diagnostic criteria for confirming suspicion of this disease. This use of ANA testing aligns with the established guidelines for screening and diagnosing autoimmune diseases, including SLE.

The other laboratory tests listed do not hold the same relevance or specificity for SLE. For instance, while rheumatoid factor can be useful in diagnosing rheumatoid arthritis, it is not specific for SLE. Gel electrophoresis is more aligned with evaluating protein levels in serum, and a spectrophotometric assay generally pertains to the quantitative measurement of substances in solutions, which doesn't directly relate to the autoimmune