Surveillance for <i>Chlamydia trachomatis</i> variants escaping detection with the Aptima Combo 2 assay in Canada from 2019 to 2021

Molecular tests are commonly used for the detection of sexually transmitted infections (STIs) like <i>Chlamydia trachomatis</i>. Mutations impacting <i>C. trachomatis</i> molecular target detection on the Hologic Panther AC2 assay have been reported in several countries, raising concerns about potential false negative results. This study showed <i>C. trachomatis</i> target detection failures in specimens submitted for <i>C. trachomatis</i> testing in Canadian laboratories from 2019 to 2021. A reformulated version of the AC2 molecular test is now available that can identify <i>C. trachomatis</i> strains harboring target site mutations that were impacted by the previous test formulation. While target site mutations were rare in Canada, revealing their presence is important to ensure accurate molecular detection of <i>C. trachomatis</i> with existing testing methods. This study supports ongoing genetic monitoring of <i>C. trachomatis</i> molecular test target sites, as well as the use of the reformulated test to avoid false negative results and subsequent transmissions.