My doctor ordered an ANA test because of chronic low white blood count, fatigue, and pain. My results were positive 1:160 homogeneous. They then did a connective tissue cascade which said my ANTINUCLEAR AB was 1 U and my CCP AB was <15.6. (20 is high normal) The test said they would not test for dsDNA or ENA antigens unless my ANTINUCLEAR AB results were at least 3 U...so my doctor says that actually my test results are negative for autoimmune. I thought I read somewhere that 1U is equivalent to a 1:160 result, but that would mean they wouldn't test for dsDNA or ENA unless my results were 1:480, which doesn't seem to make sense to me. It seems like plenty of people are diagnosed with 1:160/1:320 ANAs... Can anyone help me interpret this?
Generally a reading less than 1:80 (1 part plasma with 8 parts diluting solution (fluid)) is read as a negative ANA.
1:80 is considered a "low positive" and is not confirmatory of any disease. More tests are usually required to confirm the diagnosis. Most of people with 1:80 ANA do not have SLE or any other autoimmune disorder. However all results have to be clinically co-related. So if there are symptoms of an autoimmune disorder at 1:80, then this can be taken as confirmatory for disease.
1:320 is a definite positive and mean the disease is active.
1:640 is considered very high and tissue damage is imminent.
What is important is the pattern of ANA staining: homogenous, speckled, or nucleolar. Depending on the pattern of ANA staining, other antibody tests will have to be done. The pattern of staining itself is quite diagnostic (for eg in SLE a homogenous pattern is seen, nucleolar pattern in scleroderma and speckled pattern in ITP and mixed connective tissue disorder and in lupus)
So, since you have a homogenous pattern, it is quite specific for Lupus or SLE. You need further tests like Anti-dsDNA,Anti-ssDNA,and Anti-Smith. The connective tissue cascade is interpreted as < or =1.0 U (negative). So that way the doctors are right. However, if you have symptoms of lupus, then you need further testing. Take care!
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