Usefulness of New Automated Treponemal Tests in the Diagnosis of Early Syphilis: A Series of 15 Cases

Background Syphilis is a sexually transmitted infection caused by Treponema pallidum, subspecies pallidum. As these bacteria are difficult to culture, syphilis must be diagnosed by serologic testing. The introduction of automated treponemal tests has led to changes in the traditional diagnostic algorithm for syphilis, which began with a nontreponemal test. We present 15 cases of primary syphilis detected using these new tools and review the microbiologic techniques used for the diagnosis of early syphilis. Material and methods We examined all cases of syphilis diagnosed in our department between January 2013 and September 2018 and selected patients with negative nontreponemal (rapid plasma reagin [RPR]) tests. Results Of the 158 patients diagnosed with syphilis during the study period, 15 had a negative RPR test, and 14 of them had a positive treponemal test. Fourteen of the patients were men and ages ranged from 22 to 60 years. Polymerase chain reaction was used to detect T pallidum in the lesion exudate from 8 patients and was positive in all cases. The 15 patients were treated with a single injection of 2.4 million units of benzathine penicillin G. Conclusion Chemiluminescence immunoassays and T pallidum automated enzyme-linked immunoassays are useful in the diagnosis of early syphilis, and we believe that they should be adopted as screening tools given their diagnostic sensitivity, speed, and low cost.