DIAGNOSTICS

Evaluation of real time polymerase chain reaction assays for confirmation of Neisseria gonorrhoeae in clinical samples tested positive in the Roche Cobas Amplicor assay

S N Tabrizi¹, S Chen¹, M A Cohenford², B B Lentrichia², E Coffman², T Shultz³, J W Tapsall³ and S M Garland¹

¹ Department of Molecular Microbiology, The Royal Women’s Hospital, Victoria 3053, Australia
² CYTYC Corporation, 85 Swanson Road, Boxborough, MA 01719, USA
³ Department of Microbiology, South Eastern Area Laboratory Services, The Prince of Wales Hospital, Randwick, New South Wales 2031, Australia

Correspondence to:
Correspondence to:
Sepehr Tabrizi
PhD, Department of Molecular Microbiology, The Royal Women’s Hospital, 132 Grattan Street, Carlton, Victoria 3053, Australia; Sepehr.Tabrizi{at}wch.org.au

Objective: Development of a rapid, sensitive, and accurate assay for confirmation of Neisseria gonorrhoeae in clinical samples.

Method: Two real time polymerase chain reaction (PCR) assays, developed on the LightCycler for amplification of the N gonorrhoeae cppB gene, were utilised for confirmation of this bacterial pathogen in samples positive by the Roche Cobas Amplicor assay. Performance characteristics of the two assays were compared with other commercial nucleic acid amplification assays, including the Abbott LCx and Roche 16S rRNA tests.

Results: All related Neisseria as well as other bacterial species tested negative by both cppB gene based assays, whereas 120 N gonorrhoeae clinical isolates from various geographical regions gave in positive results. Both assays had a sensitivity of one copy per reaction. 122 clinical samples positive and another 50 samples negative for N gonorrhoeae by Roche Cobas Amplicor were selected from a specimen pool of more than 3000 women tested previously. Overall, 73 of 122 (59.8%) samples were confirmed as positive. The two real time assays had sensitivities of 99% and 100% and specificities of 98% and 100%, respectively. The 16S and LCx assays produced similar results to the real time assays, indicating a similar sensitivity to and specificity of both real time assays.

Conclusion: The data from this study highlight the need to confirm N gonorrhoeae positive Cobas Amplicor PCR results as an important part of the testing algorithm of all diagnostic laboratories utilising this assay.

Keywords: real time polymerase chain reaction; molecular detection; Neisseria gonorrhoeae

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