Serological Testing For Syphilis. Then there are serological tests. These tests are considered to be more reliable. Of course, the type of serological test for syphilis that is administered depends upon the stage of the disease.Serological testing for syphilis for syphilis can be classified into two categories—treponemal and non treponemal.or confirmation of an active infection, a person needs to take either an RPR or VDRL test. Bottom-line, both types of serologic tests for syphilis are equally important in screening and diagnosing syphilis.