National scale-up of etiological testing for N. gonorrhoeae and C. trachomatis in South Africa: a health economic modelling analysis

BackgroundNeisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) remain highly prevalent in South Africa, where syndromic management is the standard-of-care (SOC) for sexually transmitted infections (STIs). However, syndromic management lacks diagnostic precision leading to both under-treatment and excess antibiotic use, which contributes to antimicrobial resistance (AMR). With a novel lateral flow assay (LFA) for NG approaching market entry and an extensive existing GeneXpert network in South Africa, there is an opportunity to shift towards etiology-informed management of STIs. MethodsWe developed a static cohort model to evaluate the health and economic outcomes of scaling up testing for NG/CT across symptomatic and opportunistic screening pathways in South Africa. Scenarios included syndromic management, GeneXpert testing, and hypothetical NG/CT point-of-care tests (POCTs). Outcomes assessed included cases treated, quality-adjusted life years (QALYs) gained, excess antibiotic use, and cost-effectiveness. ResultsSyndromic management produced the poorest health outcomes and highest antibiotic overuse. POCTs achieved the best health outcomes and were cost-effective compared to SOC, with an incremental cost-effectiveness ratio (CER) of US$1,083-$3,497 per QALY gained. GeneXpert, though dominated overall, could be considered cost-effective for testing of symptomatic women (Average CER: US$5,073). Diagnostic testing had the greatest benefit among women due to poor sensitivity of syndromic management. Opportunistic screening using a NG-only POCT during antenatal care, family planning clinics or HIV-related services was also found to be cost-effective. ConclusionDespite higher costs, etiological testing offers significant benefits over syndromic management-- particularly for women--by improving diagnostic accuracy, reducing unnecessary antibiotic use, and supporting antibiotic stewardship. As South Africa considers introducing new treatments like zoliflodacin, investment in diagnostic testing is essential to preserve treatment efficacy and reduce long-term STI burden.