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Clinical Validation of a Real-Time Polymerase Chain Reaction Detection of Neisseria gonorrheae porA Pseudogene Versus Culture Techniques

Hjelmevoll, Stig Ove MSc*; Olsen, Merethe Elise MLT*; Sollid, Johanna U.Ericson PhD; Haaheim, Håkon MSc, MM*; Melby, Kjetil K. MD, PhD; Moi, Harald MD, PhD§; Unemo, Magnus PhD; Skogen, Vegard MD, PhD¶#

Sexually Transmitted Diseases: May 2008 - Volume 35 - Issue 5 - p 517-520
doi: 10.1097/OLQ.0b013e3181644bc9

Background: Diagnosing Neisseria gonorrheae using nucleic acid amplification tests (NAATs) might increase the sensitivity, compared to cultivation. However, using NAATs has also been problematic mainly due to the close genetic relationships between different Neisseria species, resulting in false positive diagnoses. This study was conducted to clinically validate a previously published real-time polymerase chain reaction (PCR) method targeting the porA pseudogene in N. gonorrheae in comparison to culture techniques.

Methods: In total, 360 samples, urethra (n = 109), rectum (n = 84), pharynx (n = 119), and cervix (n = 48) from 185 males and 57 females, were analyzed using porA pseudogene PCR and cultivation. Sequencing of the entire porA pseudogene and the 16S rRNA gene were used to resolve discrepant results.

Results: Of the 360 samples, 37 were positive by both culture and PCR, however, the PCR identified 15 additional confirmed positive samples. The PCR method showed a sensitivity, specificity, positive predictive value, and negative predictive value of 100% in a preselected population. The preselected population had a true gonorrhea prevalence of 17.4%.

Conclusions: The present porA pseudogene real-time PCR comprises a valuable supplement to the traditional culture techniques for diagnosis of N. gonorrheae, especially for samples from extragenital sites such as pharynx and rectum.

A study of the performance of a porA targeting diagnostic PCR for detecting Neisseria gonorrhoeae from genital as well as extra genital sites with excellent sensitivity and specificity.

From the *Department of Microbiology and Infection Control, University Hospital of North Norway; and †Department of Microbiology and Virology, Institute of Medical Biology, University of Tromsø, Tromsø; ‡Department of Microbiology, Ullevål University Hospital, Oslo, Norway; §Olafiaklinikken, Universitetet i Oslo, Norway; ∥National Reference Laboratory for Pathogenic Neisseria, Department of Clinical Microbiology, Örebro University Hospital, Örebro, Sweden; ¶Department of Internal Medicine B, University Hospital of North Norway; and #Institute of Clinical Medicine, University of Tromsø, Tromsø

This work was supported by the Department of Microbiology at the University Hospital of North Norway, Tromsø, Norway. Special thanks to the staff and colleagues at Olafiaklinikken, Oslo, Norway who took extra samples from their patients and to the patients who kindly agreed to be enrolled in our study. The authors thank Dr Amir Moghaddam for a critical review of this manuscript.

The present study was performed at the Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway.

Correspondence: Stig Ove Hjelmevoll, MSc, Department of Microbiology and Infection Control, University Hospital of North Norway, N-9038 Tromsø, Norway. E-mail:

Received for publication September 6, 2007, and accepted December 4, 2007.

© Copyright 2008 American Sexually Transmitted Diseases Association