Changing ANA manifested as seroconversion from a negative to positive ANA status, increasing titers, and changing antibody specificities can occur with certain treatments (especially Prednisone).
The antinuclear antibody test is performed with different techniques in different laboratories; some techniques are more sensitive than others, such that one laboratory may find a (usually weak) positive test while another finds it negative. Some laboratories dilute 10-fold for screening (1:10), some as much as 100-fold (1:100), and some not at all. A commonly used method starts with a dilution of 1:10, then doubles with every successive dilution, so the next specimen tested is 1:20, then 1:40, 1:80, etc., the highest number positive being what the laboratory reports (for instance, 1:1280).
Most lupus patients have sera that react at very high dilutions, essentially always more than 1:80, often more than 1:5120. Depending on the laboratory's reporting habits, a test that is positive at 1:10 or even 1:40 may be called either negative or weakly positive. Most laboratories count 1:80 and higher as clearly positive. The point is that ANA-negative does not always precisely mean completely negative. Another point is that speckled (as opposed to diffuse or peripheral) ANA patterns do not read well in automated immunofluorescence tests, so may be reported as lower titer or negative than they would be if they were hand read by an experienced technician
As you can see, there are so many factors that could be causing the changes in your ANA titers. It might be beneficial if you ask your doctor about the negative ANA.
I'm sorry I can't be more helpful to you, but the variables are too great and you should have a professional discuss your personal case with you. :cry:
Peace and Blessings
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