Can the Swedish new variant of Chlamydia trachomatis (nvCT) be detected by UK NEQAS participants from seventeen European countries and five additional countries/regions in 2009?

In 2006, a new variant of Chlamydia trachomatis (nvCT) was reported in Sweden. The nvCT contains a deletion that includes the targets for the C. trachomatis genetic diagnostic single-target systems from Roche Diagnostics and Abbott Laboratories. Roche and Abbott have now developed certified dual-target assays that can detect the nvCT. This study examined the nucleic acid amplification tests (NAATs) currently used (in 2009) for C. trachomatis detection in laboratories from 17 European countries and five countries/regions outside Europe that are participating in the United Kingdom (UK) National External Quality Assessment Service (NEQAS). It further examined changes in these laboratories' testing strategy during the period from 2006 to 2009, and their performance regarding nvCT detection. A UK NEQAS blinded nvCT specimen was distributed to all 283 participating laboratories, which were asked to analyse the specimen according to their routine C. trachomatis diagnostic protocols for endocervical swabs. BD ProbeTec was the most commonly used NAAT, followed by Cobas Amplicor, Cobas TaqMan, and Aptima. From 2006 to 2009, the use of Cobas Amplicor, which does not detect the nvCT, decreased, but it was still used by 22% (n=57) of responding participants in 59% of the countries, 54 of these 57 used it as first assay. Virtually all of the other participants detected the nvCT correctly. Laboratories using commercial or in house NAATs that do not detect the nvCT are encouraged to carefully monitor their C. trachomatis incidence, participate in effective internal and external quality assurance and controls schemes, and to consider changing their testing system. .