What specific test result is most indicative of systemic lupus erythematosus?

The presence of positive anti-Smith antibodies is a highly specific test result for systemic lupus erythematosus (SLE). These antibodies are directed against the Smith antigen, which is a protein complex found in the nucleus of cells and is associated specifically with lupus. While some anti-nuclear antibodies (ANAs) can be present in various autoimmune diseases, anti-Smith antibodies demonstrate a strong correlation with SLE. The identification of these antibodies can assist healthcare providers in confirming a diagnosis of lupus, especially when considered alongside clinical symptoms.

In contrast, a low white blood cell count might be seen in various conditions or infections and isn't specific to lupus. The presence of rheumatoid factor is more commonly associated with rheumatoid arthritis and can be found in several other conditions, therefore it lacks specificity for SLE. Lastly, high levels of hemoglobin would not typically indicate lupus, as anemia is more commonly encountered in this condition due to various factors, including hemolysis or bone marrow suppression. Thus, anti-Smith antibodies serve as a crucial indicator for systemic lupus erythematosus.