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Clinical sciences oral session 3—diagnostic testing: chlamydia & gonorrhoeae
O3-S3.05 Chlamydia trachomatis detection by nucleic acid amplification assay using rectal swabs
  1. J Williams1,
  2. B Van Der Pol2,
  3. A Pantone1
  1. 1Indiana University School of Medicine, Indianapolis, USA
  2. 2Indiana University Shool of Public Health, Bloomington, USA

Abstract

Background Rectal infection with C trachomatis (CT) is increasing in many settings; however, there are currently no FDA approved NAAT for use with rectal specimens. Access to reliable diagnostics using rectal specimens is critical to both surveillance and disease management and control. This is important as CT culture has been shown to have lower sensitivity, 54.8 %, when compared to NAAT in our patient population. The objective of this study was to evaluate the performance of rectal swabs tested on the Abbott m2000 (m2000) as compared to the GenProbe APTIMA Combo 2 (AC2) for detection of CT.

Methods Rectal samples were collected and placed into chlamydia transport medium (CTM) for testing by both m2000 and AC2 for CT. CTM was split as follows; 1 ml into an empty m2000 tube; 100 ul into m2000 multi-collect tube containing buffer; 100 ul into an AC2 swab collection tube. From this point forward, testing was performed according to the package insert for both platforms with two CT negative samples being tested for every positive one. ĸ scores were determined to measure agreement between the m2000 and AC2 collection tubes.

Results A total of 59 samples were tested for CT by m2000 and AC2. AC2 was considered the reference standard for this study with 20 samples identified as positive and 39 as negative for CT. Neat CTM placed into an empty m2000 tube detected 95% (19/20) and had a single positive that was not detected by AC2 (38/39 agreed). The single neat CTM missed by m2000 was positive in the spiked multi-collect tube. CTM spiked into an m2000 multi-collect tubes also detected all but one of the infections identified by AC2 (19/20) and negatives agreed completely (39/39). The m2000 multi-collect miss was CT positive in the neat sample. Both collection methods on the m2000 generated results that had very good agreement with the reference test: ? scores were 0.924 for empty and 0.962 for multi-collect tubes.

Conclusion The m2000 has excellent performance characteristics compared to AC2 for the detection of CT. NAATs offer an alternative to culture for the detection of CT in rectal samples, and are less susceptible to transport conditions and sterility that are often a concern with culture. The collection of rectal specimens in CTM offers the opportunity for routine testing using multiple collection devices and platforms with the data suggesting that the m2000 assay can be used to meet the revised CDC recommendations for rectal testing for CT.

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