(P78) Development of a lateral flow assay for the detection of Neisseria gonorrhoeae to support aetiological patient management and to ensure antibiotic stewardship

Background
Neisseria gonorrhoeae (NG) has become highly resistant due to decades of unnecessary antibiotic use, mainly linked to the syndromic management of sexually transmitted infections in the absence of affordable point-of-care testing. WHO and FIND published a Target Product Profile (TPP) describing the characteristics required for a low-cost NG test for use in low-resource settings.

Methods
An NG lateral flow assay (NG LFA) has been developed in partnership with DCN Dx to detect NG in male urine and female vaginal swabs. Inclusivity and limit of detection (LOD) studies were performed using well-characterized NG species (n =31). Exclusivity studies were performed using common commensal microorganisms known to inhabit the urogenital tract as well as other Neisseria bacteria (n=31). Clinical performance was then evaluated at two sites in Birmingham, Alabama, using fresh and frozen clinical specimens. Male urine samples (n=51) and female vaginal swabs (n=41) were tested using the NG LFA with the COBAS® AMPLICOR (CT/NG) as the comparator.

Results
Performance with in-house frozen clinical samples (n=40) demonstrated a sensitivity and specificity of 97.5% and 100% respectively. Inclusivity studies detected all spiked Neisseria gonorrhoeae species. Exclusivity testing showed no cross-reactivity with 28 commensal microorganisms and Neisseria species, however, cross-reactivity was observed with N. meningitidis, N. lactamica and N. polysacchareae. Observed LOD with two reference strains was 1-5 x 10³ CFU/ml. The NG LFA was positive in 11/14 (78.6%) women with a positive COBAS test for Ct < 42, and in 11/12 (91.7%) for Ct < 35; the NG LFA was positive in 12/12 (100%) men with positive COBAS test. The NG LFA was negative in 27/27 (100%) women and 35/39 (89.7%) men with a negative COBAS test, respectively. A recent statistically powered clinical evaluation in South Africa demonstrated superior performance with sensitivities of 96.1% and 91.7% and specificities of 97.2% and 96.3% in symptomatic males and females, respectively.

Conclusion
This pilot study describes the development of an NG LFA with good performance, with subsequent clinical studies demonstrating excellent performance that meets the specifications of the TPP. This novel, low-cost, rapid, and easy-to-use assay could support the shift in STI patient management guidelines from a syndromic to an aetiological approach.