Abstract
The Finnish new variant of Chlamydia trachomatis (FI-nvCT) is escaping diagnostics in Finland, Norway and Sweden. We have developed and validated an Aptima-format nucleic acid amplification test (NAAT) designed specifically to detect the FI-nvCT. This NAAT has high sensitivity (100%) and specificity (100%) for the FI-nvCT strain, enabling further investigation of the geographic distribution, prevalence and transmission of this diagnostic-escape mutant in screening populations in Europe.
Highlights
The Finnish new variant of Chlamydia trachomatis (FI-nvCT) is escaping diagnostics in Finland, Norway and Sweden
To understand the geographic distribution, prevalence and transmission dynamics of the FI-nvCT strain nationally and internationally, we have developed an Aptima-format nucleic acid amplification test (NAAT) that sensitively and detects FI-nvCT (23S rRNA gene C1515T mutation) but not wild-type (C1515) C. trachomatis strains
All validation and verification studies of the new FI-nvCT assay were conducted according to Clinical Laboratory Standards Institute (CLSI) standard protocols used for in vitro diagnostic assay validation [6]
Summary
Validation of an Aptima-format Finnish new variant of Chlamydia trachomatis (FI-nvCT) surveillance assay, 2019. In February 2019, investigation of discrepant nucleic acid amplification test (NAAT) results led to the discovery of a new genetic variant strain of Chlamydia trachomatis in south-western Finland [1] This strain, designated Finnish new variant of C. trachomatis (FI-nvCT), harbours a single nt base mutation (C1515T; Escherichia coli numbering) in 23S rRNA. This mutation was determined to be the root cause for compromised detection of the organism by the Aptima Combo 2 (AC2) diagnostic test (Hologic Inc., San Diego, California, United States (US)), which targets C. trachomatis 23S rRNA [2,3]. We have developed and validated a research-use only Aptima-format surveillance NAAT designed to detect the FI-nvCT strain This assay should facilitate further investigations to determine the geographic distribution, prevalence and transmission of this diagnostic-escape mutant. The collection consisted of 266 specimens (endocervical and vaginal swabs, male and female urine, PreservCyt ThinPrep liquid cytology) positive for C. trachomatis by the AC2 assay, and 188 specimens (mixed types) that were AC2-negative
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