Evaluation of the Elecsys Syphilis Immunoassay for Detection of Syphilis in Populations at Risk of Disease in the US and Argentina

Screening for Syphilis Infection During Pregnancy: US Preventive Services Task Force Reaffirmation Recommendation Statement

Importance

Untreated syphilis infection during pregnancy can be passed to the fetus, causing congenital syphilis. Congenital syphilis is associated with premature birth, low birth weight, stillbirth, neonatal death, and significant abnormalities in the infant such as deformed bones, anemia, enlarged liver and spleen, jaundice, brain and nerve problems (eg, permanent vision or hearing loss), and meningitis. In 2023, there were 3882 cases of congenital syphilis in the US, including 279 congenital syphilis-related stillbirths and neonatal/infant deaths, the highest number reported in more than 30 years.

Objective

The US Preventive Services Task Force (USPSTF) commissioned a reaffirmation evidence update focused on the benefits and harms of screening for syphilis infection in pregnancy.

Population

Adolescents and adults who are pregnant.

Evidence Assessment

The USPSTF concludes with high certainty that screening for syphilis infection in pregnancy has a substantial net benefit.

Recommendation

The USPSTF recommends early, universal screening for syphilis infection during pregnancy; if an individual is not screened early in pregnancy, the USPSTF recommends screening at the first available opportunity. (A recommendation).

Performance of Treponema pallidum recombinant proteins in the serological diagnosis of syphilis

Syphilis serodiagnosis is challenging because distinct clinical forms of the infection may influence serological performance and discordant results between tests make clinical decisions difficult. Several recombinant Treponema pallidum-proteins have already been tested for syphilis diagnosis and they are critical to achieve high accuracy in serological testing. Our aim was to assess the varied from performance of T. pallidum-recombinant proteins TmpA, TpN17 and TpN47 for syphilis serodiagnosis. The proteins were evaluated using sera of 338 T. pallidum-negative, 173 T. pallidum-positive individuals and 209 sera from individuals infected with unrelated diseases. The diagnostic potential was validated by analysis of ROC curves. In the liquid microarray analyses, the ROC curve varied from 99.0% for TmpA and TpN17 to 100% for TpN47. The sensitivity score yielded values of up to 90% for TpN17, 100% for TpN47 and 80.0% for TmpA. The lowest and highest specificity values were presented by TpN47 (91.9%) and TmpA antigens (100%), respectively. TpN47 showed the highest accuracy score (95.5%) among all the recombinant proteins assayed. For the ELISA, the ROC curve was 97.2%, 91.8% and 81.6% for TpN17, TmpA and TpN47, respectively. TpN17 and TmpA yielded a sensitivity of 69.9%, while TpN47 obtained a value of 53.8%. Specificity was almost 100% for all three proteins. No cross-reaction was observed for TpN17 in the serum samples from non-bacterial infections. Regarding leptospirosis-positive samples, cross-reactivity score was varied from 8.6 to 34.6%. This is most probably due to conservation of the epitopes in these proteins across bacteria. The use of recombinant proteins in immunoassays for syphilis diagnosis was showed provide greater reliability to results of the treponemal assays. Despite the low sensitivity, the proteins showed high diagnostic capacity due to the AUC values found. However, an improvement in sensitivity could be achieved when antigenic mixtures are evaluated.