You've been given information about the criteria for a Lupus diagnoses. As I've mentioned before, doctors will not make a positive diagnosis easily for many reasons. One reason is that Lupus is one of about 80 auto-immune disorders whose symptoms all resemble each other. The diagnositc procedure is more like a process of elimination. They eliminate each of the possible diseases one by one. Also, these diseases are notorious for changing, for slowly developing symptoms, or for old symptoms to disappear only to be replaced by new ones. This is why it can sometimes take up to a year before we get a definitive diagnosis.
Anti-Nuclear A Screen-Positive
Now, a positive ANA can be found in Lupus, but other illnesses also have a positive ANA. The ANA test is ordered to help screen for autoimmune disorders. While it is most often used as one of the tests to help diagnose systemic lupus, it cannot be used to definitely diagnose or eliminate Lupus. It is one of several tests that can indicate some type of auto-immune disorder.
ANA Titer: Negative (<1:40)
To perform the ANA (antinuclear antibody) test, a blood sample is drawn from and sent to the lab for testing. Serum from the blood specimen is added to microscope slides which have commerically prepared cells on the slide surface. If the serum contains antinuclear antibodies (ANA), they bind to the cells (specifically the nuclei of the cells) on the slide.
A second antibody, commercially tagged with a fluorescent dye, is added to the mix of serum and the commercially prepared cells on the slide. The second (fluorescent) antibody attaches to the serum antibodies and cells which have bound together. When viewed under an ultraviolet microscope, antinuclear antibodies appear as fluorescent cells.
If fluorescent cells are observed, the ANA (antinuclear antibody) test is considered positive.
If fluorescent cells are not observed, the ANA (antinuclear antibody) test is considered negative.
A titer is determined by repeating the positive test with serial dilutions until the test yields a negative result. The last dilution which yields a positive result (flourescence) is the titer which gets reported.
ANA Pattern: Negative
*Although the specimen was negative for anti nuclear antibodies (ana), the presence of cytoplasmic fluorescence was noted on the hep-2000 slide. Other reactivities (e.g., anti mitochondrial antibodies or anti smooth muscle antibodies) may be responsible for this fluorescence.
An ANA report has three parts: 1) positive or negative 2) if positive, a titer is determined and reported 3) the pattern of flourescence is reported. ANA titers and patterns can vary between laboratory testing sites, perhaps because of variation in methodology used. However, these are the commonly recognized patterns:
* Homogeneous - total nuclear fluorescence due to antibody directed against nucleoprotein. Common in SLE (lupus).
* Peripheral - fluorescence occurs at edges of nucleus in a shaggy appearance. Anti-DNA antibodies cause this pattern. Also common in SLE (lupus).
* Speckled - results from antibody directed against different nuclear antigens.
* Nucleolar - results from antibody directed against a specific RNA configuration of the nucleolus or antibody specific for proteins necessary for maturation of nucleolar RNA. Seen in patients with systemic sclerosis.
Now, in the absence of a positive ANA pattern and titer, it happens often that the patient will have anti mitochondrial antibodies or anti smooth muscle antibodies, which is indicative of an auto-immune disease and possibly of Lupus.
It does not happen often that a person has a low titer positive ANA, but it does occur and should not be ignored by doctors. Unfortunately some of the people with low titer positive ANAs do have diseases! The problem with diagnosing these diseases is that doctors MUST consider the following: Positive predictive value – how likely is it that a positive test means you do have the disease. Negative predictive value – how likely is it a negative test means you don’t have disease! Neither one can be taken as gospel. Further tests must be done!
The results depend entirely on the person being tested. If doctors are testing someone with symptoms whom they suspect have a disease, they will get entirely different results than if they randomly test people on the street with no reason to suspect they have disease. Thus the sensitivity, specificity, etc all depend on the clinical situation of the person being tested.
The general guidelines that should be used are 1) If the patient has symptoms of a rheumatic/atuo-immune disease, they should be evaluated no matter what the ANA result.
2) If the patient has an ANA of 1:40 or less, it cannot be assumed that this means nothing. If the ANA is 1:80 you are in ‘no man’s land.’ (it could mean any number of things!); If the ANA is 1:160 or higher, a rheumatologist should take a closer look and do further testing.
I hope that I've answered some of your questions and that I did not confuse you further. Please let me know if you need anything further!
Peace and Blessings
Look For The Good and Praise It!