What First To Know is
The First To Know Syphilis Test, made by NOWDiagnostics, is a single-use lateral-flow test that detects antibodies to Treponema pallidum, the bacterium that causes syphilis, in a drop (about 40 microlitres) of fingerstick blood. It gives a result in about 15 minutes. FDA granted it De Novo authorization on August 16, 2024, as a test for antibodies associated with syphilis performed by lay users, intended for over-the-counter use "in individuals suspected of syphilis" and "not a substitute for visits to a healthcare provider" (FDA De Novo record DEN230090), and described it as the first at-home, over-the-counter test for syphilis antibodies (FDA announcement).
Accuracy in the FDA-reviewed study
In the clinical study summarized by FDA, sexually active lay users aged 18 to 64 at six sites ran the test themselves in a simulated home setting, with observers present but not helping. Their results were compared with laboratory testing of a blood sample from a vein, using two treponemal tests and one nontreponemal test. Among 1,270 paired results, the test detected 93.4% of positives (99 of 106) and correctly cleared 99.5% of negatives (1,158 of 1,164). FDA reports an invalid rate of 5.6% (75 of 1,345 tests). In a separate laboratory panel (stored serum, not fingerstick use), all 125 samples from people with primary, secondary, early latent or late latent syphilis tested positive (FDA decision summary DEN230090).
These results were also published in a peer-reviewed journal by authors who all worked for NOWDiagnostics PMID: 40762507. No independent accuracy study was found, which is why the test carries a lower evidence grade than OraQuick here. A 2023 systematic review of syphilis self-testing found that 88% of people offered kits used them, but no sensitivity or specificity data for syphilis self-tests at that time PMID: 37482070.
Why past infection matters
First To Know detects treponemal antibodies, which usually persist. FDA's authorization states that results will likely be positive for people previously diagnosed with syphilis, even if they were successfully treated, and that the test cannot determine whether there has been reinfection (FDA decision summary). CDC's treatment guidelines note that most people with a reactive treponemal test stay reactive for life, and that relying on only one type of syphilis blood test can miss primary syphilis or give false positives (CDC STI Treatment Guidelines: Syphilis).
FDA's review also found occasional false positives in samples with Epstein-Barr virus antibodies or rheumatoid factor, and invalid results with high levels of gamma-globulin (FDA decision summary).
Is First To Know right for you?
Consider First To Know if you have never been diagnosed with syphilis and want a private screening test at home. It does not test for HIV or other infections; our at-home STD testing guide compares it with the OraQuick HIV test and explains other options.
See a clinician instead if you have had syphilis before, are pregnant (CDC recommends syphilis testing early in pregnancy; see CDC: Getting Tested for STIs), or have a genital sore or rash. Any positive result needs laboratory testing through a health care provider before a diagnosis or treatment decision. CDC's GetTested locator lists free or low-cost, confidential testing near you.