Evaluation of a novel point-of-care lateral flow assay screening for Neisseria gonorrhoeae infection among pregnant women in Zimbabwe

Abstract

Affordable, easy-to-use and rapid diagnostics may support a move away from syndromic management for sexually transmitted infections (STIs) in resource-constrained settings. A lateral flow assay for Neisseria gonorrhoeae (NG-LFA) has shown high sensitivity and specificity (>90%) in symptomatic individuals. We investigated the performance and acceptability of this assay as a screening tool for NG among pregnant women. This evaluation was embedded within a prospective study evaluating point-of-care STI screening in pregnant women attending antenatal care (ANC) in Harare, Zimbabwe. Participants were included regardless of symptom status, ANC visit number, or gestational age. Nurse-collected vaginal swabs were tested on-site using the NG-LFA and the Xpert CT/NG assay (Xpert) (reference test). The implementation team members (n=4) were interviewed to assess acceptability and usability of NG-LFA. Of 912 participants, 4.8% (44/912) self-reported presence of abnormal vaginal discharge. Xpert NG prevalence was 4.2% (38/912); 81.6% (31/38) of infections were asymptomatic. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of the NG-LFA were 65.8% (25/38; 95% CI 48.6%-80.4%), 99.2% (867/874; 95% CI 98.4-99.7%), 78.1% (25/32; 95% CI 60.0-90.7%), and 98.5% (867/880; 95% CI 97.5-99.2%). The NG-LFA was considered easy-to-use and interpret but discordant results led to issues of trust in the NG-LFA results. Among predominantly asymptomatic pregnant women, the NG-LFA had high specificity, but relatively low sensitivity meaning one in three cases of gonorrhoea were not detected. Further studies are warranted to assess the clinical performance and cost-effectiveness of the NG-LFA in other settings and populations.