How accurate is treponemal tests like tppa, tpha, tpla after 4 weeks of exposure?

At four weeks a positive result would be definitive. To rule out infection, you should repeat the test at 6 weeks after exposure. The average window period or incubation period for syphilis is about three to six weeks. If you get tested earlier than this period, you should test again within the window period to confirm your results.

These tests should not be used to diagnose syphilis or screen for infection. They are intended only for use in confirming results of other syphilis blood tests, like RPR, VDRL, or EIA tests. Whether or not properly used, they probably can take 6 weeks or maybe even 8-10 weeks to be positive. They would miss many infections at 4 weeks.