Are rapid syphilis tests always reliable? is it true that they often give false negatives?

All syphilis blood tests take a few weeks to become positive. But after 3 months, false negatives do not occur with the rapid tests (or other tests based on the same antibody, like EIA tests). If you were potentially infected more than 3 months ago, your negative result proves you do not have syphilis and never did. If before 3 months, have another test after that much time has passed.

Testing too early may give a negative result despite infection. Repeat the test at three months after exposure. An other reason for a false low reading is a very high anybody titer,beyond the linear range of the test. If you are in the secondary phase or syphilis infection your doctor should ask the laboratory to run a titer of antibody.