What laboratory test is most indicative of systemic lupus erythematosus (SLE)?

The most indicative laboratory test for systemic lupus erythematosus (SLE) is the antinuclear antibody (ANA) test. This test is highly sensitive for SLE, meaning that a significant number of patients with this condition will have a positive result. ANAs are autoantibodies that target the cell nucleus and are found in a variety of autoimmune disorders, but their presence is especially prevalent in SLE patients.

Given that SLE is a complex autoimmune disease characterized by a wide range of clinical manifestations, the ANA test serves as an essential screening tool. A positive ANA test does not confirm SLE by itself, as other conditions can also present with elevated ANA levels. However, it is a crucial first step in the diagnostic process for SLE because a negative ANA usually rules out the disease.

While the sedimentation rate and C-reactive protein tests can indicate inflammation, they are not specific to SLE and can be elevated in various other inflammatory conditions. Similarly, while there are tests that are specific for SLE, the ANA is the most commonly used and recognized initial laboratory test indicative of the disease due to its high sensitivity. Therefore, the selection of the ANA test aligns well with established diagnostic protocols for SLE.