Any test for syphilis is quite accurate 6 weeks after the encounter, but there are people that take longer to show a positive result, so it's always interesting to repeat the test 3 months after the encounter if t result is negative.
Regarding test in general, it doesn't really matter which kind of test we are using or which std we are testing for. If we expire the window period before testing, the result will be accurate up to 99.99%