What is a common laboratory test for diagnosing lupus?

The antinuclear antibody (ANA) test is a common laboratory test used to help diagnose lupus, which is also known as systemic lupus erythematosus (SLE). This autoimmune disease is characterized by the body’s immune system attacking its own tissues, and the presence of antinuclear antibodies in the blood is a key indicator. A positive ANA test suggests that the immune system may be producing antibodies against the body's own nuclear material, which is commonly associated with lupus and other autoimmune conditions.

The other tests listed, while valuable in their own contexts, do not specifically diagnose lupus. A complete blood count can reveal anemia or other blood parameters but is not specific for lupus. The CRP (C-reactive protein) test measures inflammation in the body but cannot indicate the presence of lupus itself. Similarly, the blood glucose test is primarily used to assess glucose levels and diabetes management, bearing no relevance to lupus diagnosis. Thus, the antinuclear antibody test stands out as the critical tool for identifying this specific autoimmune condition.