During the hard chancre phase of syphilis, a portion of cases can test positive for Treponema pallidum, although some tests may return negative results. In such cases, it is advisable to retest after one month.

The earliest detectable antibodies for Treponema pallidum are usually of two types: a Treponema pallidum-specific antibody, which appears earlier than the non-specific antibodies. There are tests for non-specific antibodies, commonly referred to as RPR or TRUST, which are standard practices in major hospitals.

Therefore, in early-stage syphilis or primary syphilis with hard chancre, it is possible to find Treponema pallidum-specific antibodies positive, RPR or TRUST negative, or both negative. If syphilis is strongly suspected in such cases, a retest is recommended after one month.