The value of the ana test is determined by lots of factors. The results of an ANA test are usually given in titres, which is a measure of how much the blood sample can be diluted before the presence of the antibodies can no longer be detected
Normal Levels: (normal values may vary from lab to lab)
Titers of 1:20 or 1:40 or less are generally considered normal depending on the lab and methods used to conduct the test.
Some information states that a normal titre of 1:40 or less is normal, whilst other information states that a titre of 1:80 or lower is usually considered negative. Also results can vary from lab to lab.
A negative ANA argues pretty strongly against Lupus but it does not completely rule it out. Infrequent cases of SLE patients with negative ANAs can be found when positive Anti-Ro (SSA) or
A positive ANA does not automatically mean Lupus, once again other clinical findings must be taken into account. The reason for this is because a positive ANA can also be found in many other autoimmune diseases such as Multiple Sclerosis, Autoimmune Thyroiditis, Scleroderma, Sjogren's Syndrome, Autoimmune Hepatitis, and Rheumatoid Arthritis. This test can also be positive in people with some infectious diseases like mononucleosis, chronic hepatitis, malaria and lepromatous leprosy. There are certain drugs such as isoniazid, procainamide, chlorpromazine, and hydralazine can cause a positive ANA also. 30-40% of first degree relatives of SLE patients will have a positive ANA and no symptoms. Finally, as many as 20% of completely healthy individuals will also have a positive ANA.
The titer is a ratio that expresses the number of times the technician had to dilute the plasma from the blood before the antibodies could no longer be detected. In other words, a titer of 1:40 would mean that the antibodies were last detected when 1 part of the blood was diluted with 40 parts of either water or saline. The higher the second number the higher the concentration of antibodies. Since the amount of dilution fluid is doubled the titers can increase rapidly from 1:40 to 1:80 to 1:160 to 1:320 to 1:640 and so on. Antibodies fluctuate in concentration during the course of disease and a high or low titer does NOT indicate the level of disease activity and can not reliably be used to determine disease activity level. However, the higher the titer, the more likely an autoimmune disease is present.
These are the different patterns and what they mean:
Rim / Peripheral - found almost exclusively in people with SLE
Homogenous / Smooth - found in high titers in SLE also found in Drug-Induced Lupus, and other autoimmune diseases, also the most commonly found pattern in healthy individuals
Speckled - found in SLE, mixed connective tissue disease, Sjogren's Syndrome, Scleroderma
Diffuse - non-specific pattern
Nucleolar - found in Scleroderma, CREST Syndrome, systemic sclerosis, and sometimes SLE or Rheumatoid Arthritis
Centromere - found in PSS with CREST Syndrome, polymyositis, Raynaud's Syndrome
Hope this helps...