Which laboratory result supports the diagnosis of SLE?

The diagnosis of Systemic Lupus Erythematosus (SLE) is often supported by specific laboratory results, among which a significantly elevated antinuclear antibody (ANA) titer is a key indicator. ANAs are a group of antibodies that target the body's own cellular components, and their elevation is one of the hallmark features of SLE.

Pancytopenia, which refers to a reduction in red and white blood cells as well as platelets, can occur in individuals with SLE due to autoimmune hemolytic anemia or bone marrow involvement, making it a relevant finding in the context of SLE diagnosis. The combination of pancytopenia along with a high ANA titer strongly supports a diagnosis of SLE, as it aligns with the typical hematologic manifestations of the disease.

In contrast, other laboratory results such as leukocytosis or thrombocytosis can be seen in various other conditions and are not specific to SLE. Elevated BUN and creatinine suggest kidney involvement but are not strictly diagnostic of lupus. Therefore, while these may indicate some level of systemic involvement and complications, they do not provide the same direct support for an SLE diagnosis as the elevated ANA and the hematologic findings in option B.