Comparison of the Abbott RealTi m e CT New Formulation Assay with Two Other Commercial Assays for Detection of Wild-Type and New Variant Strains of Chlamydia trachomatis

Abstract

In an analytical-method comparison study of clinical samples, the Abbott RealTime CT new formulation assay (m2000 real-time PCR), consisting of a duplex PCR targeting different parts of the cryptic plasmid in Chlamydia trachomatis, was compared both with version 2 of the Roche Cobas TaqMan CT assay, comprising a duplex PCR for a target in the cryptic plasmid and the omp1 gene, and with the Gen-Probe Aptima Combo 2 assay (AC2) targeting the C. trachomatis 23S rRNA molecule. First-catch urine samples from Sweden were tested in Malmö, Sweden, for C. trachomatis with the m2000 real-time PCR assay and with an in-house PCR for the new variant C. trachomatis strain with a deletion in the cryptic plasmid. Aliquots of the urine samples were sent to Aarhus, Denmark, where they were further examined with the TaqMan CT and AC2 assays. A positive prevalence of 9.1% (148/1,632 urine samples examined) was detected according to the combined reference standard. The sensitivities and specificities of the three assays were as follows: for the Abbott m2000 A new variant of Chlamydia trachomatis with a deletion in the cryptic plasmid has been described in Sweden (3, 4). In a previous study. we compared the Gen-Probe Aptima Combo 2 (AC2) and Aptima CT assays, directed against different rRNA targets of C. trachomatis, with the Abbott m2000 real-time PCR assay and the Roche Cobas Amplicor CT assay. The two latter assays both target a sequence within the area deleted in cryptic plasmid of the new variant (2). We used routine samples from females and males to confirm that the new variant strain was present in one-fourth of the C. trachomatis-positive samples from the Malmö area in Sweden and that the two assays targeting the cryptic plasmid were unable to detect the plasmid mutant (2). Modifications of the Abbott m2000 and Roche Cobas assays have now been released; each consists of a duplex PCR with different targets in C. trachomatis. The new formulation of the m2000 real-time PCR adds a different target region in the cryptic plasmid to the original plasmid PCR test, and the new version 2 of the Roche Cobas TaqMan CT assay combines the original plasmid PCR with a PCR targeting the omp1 gene in C. trachomatis.The aim of this study was to compare and assess the analytical performance of the Abbott RealTime CT new formulation assay (Abbott m2000 real-time PCR clinical diagnostic system) with those of version 2 of the Roche Cobas TaqMan CT test and the Gen-Probe Aptima Combo 2 assay for clinical samples from a population with a high rate of the plasmid mutant strain. MATERIALS AND METHODSConsecutive first-catch urine samples submitted to the Department of Clinical Microbiology, Malmö University Hospital, Malmö, Sweden, and received from Monday to Thursday, from May 2008 to June 2008, were included in the study. Samples (n ϭ 1,632) were from male and female patients undergoing routine screening for C. trachomatis. Upon arrival, aliquots were transferred to the Gen-Probe and Abbott collection devices according to the respective package insert...

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Optimized testing for C. trachomatis DNA in synovial fluid samples in clinical practice

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