What laboratory test is positive in 95% of SLE cases?

The antinuclear antibody (ANA) test is a key laboratory test that is highly indicative of systemic lupus erythematosus (SLE), with a positive result occurring in approximately 95% of SLE cases. ANA are antibodies that target components within the nucleus of cells, and their presence is a hallmark of autoimmune disorders, particularly lupus. The sensitivity of the ANA test makes it an essential tool in the diagnosis of SLE, as a positive ANA can lead to further testing to confirm the diagnosis or rule out other conditions.

While a complete blood count can provide various information about blood cells and may show abnormalities in patients with SLE, it is not specific to the disease and does not have the same level of positive predictive value as the ANA test. Urinalysis can reveal signs of kidney involvement, another important aspect of SLE, but it is not used for initial screening or diagnosis of the condition. Serum creatinine levels may indicate renal function but again do not serve as a primary diagnostic test for SLE.