A positive antinuclear antibody test, or ANA test, indicates the possibility that a patient has an autoimmune disease, according to MedlinePlus. About 2 to 8 percent of healthy people also test positive, says the journal Rheumatology. The test alone cannot be used to diagnose any disease.
Patients commonly undergo ANA tests when doctors suspect the autoimmune disease systemic lupus erythematosus, commonly known as lupus, says MedlinePlus. The American Family Physician journal reports that ANA tests are positive in 99 percent of people with lupus, but also in more than 90 percent of patients with scleroderma, Sjogren's syndrome, and mixed connective tissue disease; 78 percent with polymyositis and dermatomyositis; and 40 percent with rheumatoid arthritis. All of these are considered not only autoimmune diseases, but also connective tissue diseases.
Some research has correlated multiple sclerosis with positive ANA tests, but the journal Rheumatology questions whether there is a significant relationship between this disease and antinuclear antibodies. MS is an autoimmune condition, but not a connective tissue disease. Positive ANA tests can also occur with thyroid disease and chronic liver disease, according to MedlinePlus.
Another article in the journal Rheumatology mentions that one type of antinuclear antibody can cause nephritis, or inflammation of the kidneys, a common cause of illness and death in lupus patients.