The TPHA test is a screening test done to check the presence of antibodies. Once infected, these antibodies persist in the blood for the rest of the person’s life. Non-treponemal antibodies, on the other hand, normally disappear after around 3 years in a well treated person. Therefore, a positive treponemal test (such as RPR) to distinguish between a current infection (or reinfection) and one that happened before and was effectively treated.