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P19 Measuring the impact of supplementary testing of neisseria gonorrhoea positive nucleic acid amplification tests on the rate of extra-genital neisseria gonorrhoea diagnosis and concordance of naats with bacterial culture
  1. Rachel Coyle,
  2. Michael Rayment,
  3. Sarah Creighton
  1. Homerton University Hospital, London, UK


Background/introduction Nucleic-acid amplification tests (NAATs) are more sensitive in the detection of Neisseria Gonorrhoea (NG) than culture or microscopy, but specificity at extra-genital sites may be lower due to cross reactivity with other Neisseria species. BASHH recommends supplementary testing of NG positive extra-genital NAATs to improve specificity. This inner city DGH introduced supplementary testing on 01/11/13.

Aim(s)/objectives To evaluate the impact of introducing supplementary testing on the rate of extra-genital NG diagnosis and concordance of positive NAATs with culture.

Methods All patients with a diagnosis of NG at any site between 01/08/13 and 31/01/14 were identified. Concordance of positive NAATs with bacterial culture pre- and post-intervention was reviewed.

Results There were 471 positive NAATs from 372 patients during the study period. Extra-genital samples accounted for 48.6% (n = 118/243) of positive NAATS pre-intervention and 41.2% (n = 94/228) post-intervention, (p = 0.03). Culture was obtained from 305 sites, 119 of which were extra-genital. Concordance pre- and post-intervention is detailed in below.

Abstract P19 Table 1

Gonorrhoea test concordance

Discussion/conclusion The proportion of NG positive NAATs from extra-genital sites fell following the introduction of supplementary testing, which may reflect an improvement in specificity. A non-significant increase in concordance of NAATs with culture was noted however concordance was low overall, especially in the pharynx. It remains unclear whether discordant results represent lower sensitivity of culture, lower specificity NAATs despite supplementary testing, or spontaneous clearance between screening and recall for culture.

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