Here is another positive ANA in which the substrate cells are a human cell line known as Hep2. A positive ANA can be reported with a titer, which gives an indication of the strength of the immune response. The titer is simply the highest dilution of patient serum at which the test is still positive. The test is typically reported as positive at greater than 1:16 or 1:20 (depending upon the laboratory) to be positive at all. In general, the higher the titer, the more likely a serious autoimmune disease is present. Thus, a 1:40 result might not mean much, but a 1:1012 certainly should not be ignored. A negative ANA, however, does not exclude a diagnosis of an autoimmune disease.