Concordance between nucleic acid amplification technique and culture for the diagnosis of gonorrhoea

Abstract

The objective of the study was to evaluate the concordance between nucleic acid amplification technique (NAAT) and culture for the diagnosis of Neisseria gonorrhoeae among attendees at a genitourinary medicine clinic in East London. All patients testing positive for N. gonorrhoeae on NAAT and/or culture between 1 April 2007 and 31 August 2008 at the Department of Sexual Health at Homerton University Hospital were included. Male patients had a first void urine sample for NAAT and urethral culture; female patients had a self-taken vulval swab or endocervical sample sent for NAAT and an endocervical culture sample. After interim analysis, discrepant results had both NAAT and culture repeated prior to treatment. Of 159 male patients with a positive NAAT, 22 (13%) had a negative culture. Among 135 female patients with a positive NAAT, 36 (27%) had a negative culture. Three men had a positive culture and negative NAAT. Nineteen of the discrepant samples were retested prior to treatment and 12 (63%) had spontaneously revered to negative. In conclusion, there was concordance in 84% of male and 67% of female samples. In two-thirds of the discrepant cases, the previously positive NAAT had become negative prior to treatment. This study highlights the importance of consideration of the clinical picture when assessing results.