What do the "titer" results for syphilis mean?
Apr 29, 2012
I have read a number of responses about syphilis testing and results, but I am totally unclear about what the titer results mean. Is 1:2 low or high? Is 1:16 better or worse than 1:8? The display of titer results in the form of a mathematical ratio has me confused, and if the numbers bounce around I cannot tell if it's getting better or worse. Please clarify!
Response from Dr. McGowan
Thanks for your question.
The titers refer to how many times you can dilute the sample and still get a positive result. So if you have lots of antibody you can water it down alot and it will still show up positive.
For example: 1:1 is no dilution. 1:2 is diluted 50%. Next is 1:4 diluted again by half. etc.
So 1:2 is a lower titer than 1:16 or 1:256 (which would be lots of antibody requiring lots of diluting to before you can no longer detect it).
After someone is treated for syphilis we like to see the titers drop after a few weeks. In order for it to be adequate the levels must change by at least 2 dilutions....so 1:16 would have to drop at least below 1:4 to show a good response to treatment. A titer that bounces from 1:2 to 1:4 would not cause concern, but if it went up by 2 steps (1:2 to 1:4 to 1:8) that would be worrisome.
Hope that helps.
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