Laboratory Tests
ANA Titers and Patterns
ANA laboratory reports include a titer (pronounced TY-tur) and a pattern.
- The titer indicates how many times the lab technician had to dilute plasma from the blood to get a sample free of the antinuclear antibodies.
- For example, a titer of 1:640 shows a greater concentration of anti-nuclear antibodies than a titer of 1:320 or 1:160.
- The apparent great difference between various titers can be misleading.
- Since each dilution involves doubling the amount of test fluid, it is not surprising that titer numbers increase rather rapidly.
- In actuality, the difference between a 1:160 titer and a 1:320 titer is only a single dilution. This does not necessarily represent a major difference in disease activity.
- ANA titers go up and down during the course of the disease, and a high or low titer does not necessarily mean the disease is more or less active.
- Therefore, it is not always possible to determine the activity of the disease from the ANA titer.
- A titer above 1:80 is usually considered positive.
- Some laboratories may interpret different titer levels as positive, so one cannot compare titers from different laboratories.
- The pattern of the ANA test can sometimes be helpful in determining which autoimmune disease is present and which treatment program is appropriate.
- The homogeneous, or smooth pattern is found in a variety of connective tissue diseases, as well as in people taking particular drugs, such as certain antiarrhythmics, anticonvulsants or antihypertensives.
- This homogenous pattern is also the one most commonly seen in healthy individuals who have positive ANA tests.
- The speckled pattern is found in SLE and other connective tissue diseases
- The peripheral, or rim pattern is found almost exclusively in SLE.
- The nucleolar pattern, with a few large spots, is found primarily in people who have scleroderma.
Because the ANA is positive in so many conditions, the results of the ANA test have to be interpreted in light of the person's medical history, as well as his or her clinical symptoms. Thus, a positive ANA alone is never enough to diagnose lupus. On the other hand, a negative ANA argues against lupus but does not rule out the disease completely.
A Positive ANA Does Not Equate to Having a Disease
The ANA should be looked at as a screening test. If it is positive in a person who is not feeling well and who has other symptoms or signs of lupus, the physician will probably want to conduct further tests for lupus.
If the ANA is positive in a person who is feeling well and in whom there are no other signs of lupus, it can be ignored. If there is any doubt, a consultation with a rheumatologist should clarify the situation.