If a patient is suspected to have Systemic Lupus Erythematosus (SLE), an antinuclear antibody test (ANA) is typically ordered as an initial blood test. The ANA test is a screening tool that is used to detect the presence of autoantibodies in the blood, which are a type of protein that attack healthy cells. A positive ANA test result can be an indicator of SLE, but it’s important to note that a negative ANA result does not rule out this condition.