Background Acute respiratory infections are a common reason for antibiotic overuse. We previously showed that providing Sri Lankan clinicians with positive rapid influenza test results was associated with a reduction in antibiotic prescriptions. The economic impact of influenza diagnostic strategies is unknown.

Methods We estimated the incremental cost per antibiotic prescription avoided with three diagnostic strategies versus standard care when managing Sri Lankan outpatients with influenza-like illness (ILI): (1) influenza clinical prediction tool, (2) targeted rapid influenza testing and (3) universal rapid influenza testing. We compared findings with literature-based estimates of the cost of antimicrobial resistance attributable to each antibiotic prescription.

Results Standard care was less expensive than other strategies across all parameter values in one-way sensitivity analyses. The incremental cost per antibiotic prescription avoided with clinical prediction versus standard care was US$3.0, which was lower than the base-case estimate of the cost of antimicrobial resistance per ILI antibiotic prescription (US$12.5). The incremental cost per antibiotic prescription avoided with targeted testing and universal testing versus standard care were both higher than the base-case cost of antimicrobial resistance per ILI antibiotic prescription: US$49.1 and US$138.3, respectively. To obtain a cost-effectiveness ratio lower than US$12.5 with targeted testing versus standard care, the test price must be <US$2.6. At a higher threshold of US$28.7, the test price must be <US$7.7.

Conclusion Clinical prediction tools and targeted rapid influenza testing may be cost-saving strategies in Sri Lanka when accounting for the societal cost of antimicrobial resistance.