Rapid risk assessment: Chlamydia trachomatis false-negative test results by Aptima Combo 2 CT/NG assay (Hologic) in the EU/EEA, 2019

A patient tested in June 2018 has been identified as the earliest case with discordant results. In laboratories using AC2 in Finland, the cases that may have been missed due to false-negative or equivocal results may amount to 6–10% of CT positive cases. 

In mid-May 2019, Hologic confirmed that a mutation in the 23S rRNA gene is the likely root cause of the discordant results and issued an Urgent Field Safety Notice in June 2019 with updated instructions for test result interpretation and reflex testing of samples to laboratories using AC2. The implementation of these measures will allow for the appropriate diagnosis and management of the variant CT. 

Two samples in Sweden have been confirmed as having the 23S rRNA gene mutation. At the time of issuing this risk assessment, additional Member States are investigating discordant AC2/ACT results.