ANA is a nonspecific lab test. It can be seen with systemic autoimmune diseases (e.g., systemic lupus erythematosus, scleroderma, Sjogren's syndrome, mixed connective tissue disease, polymyositis/dermatomyositis, and rheumatoid arthritis), organ-specific autoimmune diseases (e.g., thyroid diseases such as Hashimoto thyroiditis and Graves disease, gastrointestinal diseases such as autoimmune hepatitis, primary biliary cholangitis, and inflammatory bowel disease, and pulmonary diseases such as idiopathic pulmonary fibrosis), and infectious diseases (e.g., viral infections such as hepatitis C and parvovirus, bacterial infections such as tuberculosis, and parasitic infections such as schistosomiasis).
Other associations with positive ANA tests have been noted, including various forms of cancer (rarely), as a harbinger of the future development of autoimmune disease, various medications, and having one or more relatives with an autoimmune disease. Some individuals, even those without a relative with autoimmune disease, may have a positive test for ANA and yet never develop any autoimmune disease.
A positive test for ANA does not, by itself, indicate the presence of an autoimmune disease. Because of the design of the ANA test, many normal individuals will have a positive test at low titers. Even when detected at high titer, a positive ANA result, by itself (in the absence of symptoms or physical findings), does not indicate that a patient either has, or will develop, an autoimmune disease.
"But they never gave a titer it just says 1.7? What does that mean?"
In the IFA test (ImmunoFluorescence Assay) for ANA, they repeatedly dilute the sample from the patient until glowing ANA can't be detected anymore. The highest dilution that's still positive gives the titer. A titer of 1:2 would mean they diluted e.g. 1 milliliter of blood with 1 milliliter of saline solution. In reality, the lowest they would start with is 1:40. Usually, anything below 1:80 is considered negative. 1:160 is moderate. High is usually 1:320 (but sometimes 1:640 is the threshold, things are not in stone). They also make a judgment on the pattern seen via microscope.
In EIA (Enzyme ImmunoAssay), there is no diluting. Instead, they add an enzyme and measure the amount of change in color or brightness that occurs. The result is given in units, which are arbitrary and vary by the manufacturer. There is no pattern seen in EIA.
In a third type, MIA (Multiplex ImmunoAssay), they cleverly use very many tiny, tiny beads. The assay antibodies attach to the beads, and the beads are run in a stream through a detector. This mimics the way that Flow Cytometry is used to examine and count cells in cancer testing. That's darn clever. The result of MIA is only given as positive or negative.
Each method has advantages and weaknesses. E.g.: IFA can detect over a hundred antinuclear and anticytosolic antibodies, while EIA detects only a selected small subset of antibodies. So IFA has greater sensitivity while EIA has greater specificity. Remarkably, the two methods do not necessarily agree with each other, much more so than one would hope for. In any one patient, IFA might say 'strong' while EIA says 'negative', or vice versa. But they have the same overall accuracy. Most rheumies have regarded IFA as the gold standard.
All of that is mainly for future reference. Here are two great presentations:
Medicine Grand Rounds - Anti-nuclear antibodies (ANAs) in clinical practice 1_22_19-bFc780fygHY
Antinuclear antibody screening - Making an informed decision-yyX6pTT8U2M