If an antinuclear antibody immunofluorescence assay, or ANA INF, screen is positive, physicians next test for ANA titer and pattern, notes Quest Diagnostics. If the second set of testing is negative, the blood work report shows a positive ANA screen with a negative ANA titer.
Patients suspected of having autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis undergo testing for ANA levels, notes Lab Tests Online. Having a positive ANA result means there are antibodies present in the blood, but further testing is needed to determine which autoimmune disease is the cause of a patient's symptoms.
A positive ANA result does not mean a person has an autoimmune disease, as up to 15 percent of healthy people have positive ANA levels without any evidence of disease, explains the American College of Rheumatology.