What do blood and urine tests for systemic lupus erythematosus (SLE) usually test for?

Blood and urine tests for systemic lupus erythematosus (SLE) primarily focus on the detection of antinuclear antibodies (ANA). These antibodies are produced by the immune system and target the body's own cells, which is characteristic of autoimmune diseases like SLE. The presence of ANA is a key diagnostic marker for SLE, as they are found in a high percentage of patients with the condition. Testing for ANA is part of a larger panel of autoimmune tests and is crucial in confirming the diagnosis of SLE, along with clinical evaluation and other laboratory findings.

The other options, while useful in evaluating different conditions, do not specifically correlate with the diagnosis of SLE. Red blood cell count can indicate anemia, which may occur in SLE patients but is not diagnostic. Thyroid hormone tests are relevant for thyroid disorders but do not relate to SLE. Likewise, electrolyte level tests can help assess kidney function and hydration status but do not directly relate to the diagnosis of lupus. Thus, antinuclear antibodies stand out as the primary focus for testing in the context of systemic lupus erythematosus.