RSV Detection and Antibiotic Prescribing Decisions for Pediatric Respiratory Tract Infections.

Importance: Respiratory syncytial virus (RSV) is a leading cause of pediatric viral lower respiratory tract infections (VLRTIs), often leading to inappropriate antibiotic use. Although rapid antigen diagnostic tests (Ag-RDTs) support clinical diagnosis, their effect on antibiotic prescribing in community settings remains uncertain. Objective: To evaluate the association of RSV Ag-RDT implementation with antibiotic prescribing practices for infants and children assessed for LRTIs. Design, Setting, and Participants: This retrospective cohort study used data from a community-based primary care setting involving family pediatricians in Italy participating in the Pedianet network. Data were collected between December 2023 and May 2024 from children aged 9 to 36 months with symptoms of VLRTI who underwent RSV Ag-RDT during the 2023-2024 respiratory epidemiologic season and historical matched cohorts. Exposure: Children with RSV-positive and RSV-negative Ag-RDT results were compared with each other and with matched historical (2022-2023) and contemporaneous (2023-2024) cohorts of children with clinically diagnosed VLRTIs or bronchiolitis who did not undergo laboratory testing. Main Outcomes and Measures: The primary outcome was antibiotic prescribing within 14 days of diagnosis. Prescriptions associated with suspected or confirmed bacterial infections (such as elevated C-reactive protein levels or documented coinfections) were excluded. Relative risks (RRs) and 95% CIs were estimated using log-binomial regression models. Results: Among 256 cases (median age, 15.06 [IQR, 11.61-22.72] months; 133 males [51.95%]), 79 (30.86%) were RSV positive and 177 (69.14%) were RSV negative. These 2 groups were comparable in age, with RSV-negative children slightly younger (median age, 14.95 [IQR, 11.66-22.67] vs 15.34 [IQR, 11.40-23.10] months), and in sex distribution, with a higher proportion of females among RSV-positive cases (41 [51.90%] vs 82 [46.33%]). Antibiotic prescribing was lower in RSV-positive than RSV-negative children (0.18 [95% CI, 0.10-0.25] vs 0.29 [95% CI, 0.22-0.35] prescriptions per 10 person-days) and was associated with a reduction in risk of receiving an antibiotic prescription (RR, 0.52; 95% CI, 0.33-0.83). Implementation of RSV Ag-RDT was associated with lower antibiotic use for VLRTIs compared with a matched untested cohort (RR, 0.54 [95% CI, 0.44-0.66] in 2022-2023 and 0.61 [95% CI, 0.50-0.75] in 2023-2024) and for bronchiolitis in 2022-2023 (RR, 0.56 [95% CI, 0.33-0.95]) but not in 2023-2024 (RR, 0.75 [95% CI, 0.42-1.33]). Reductions were greater among RSV-positive cases: for VLRTIs, the RR was 0.33 (95% CI, 0.20-0.52) in 2022-2023 and 0.41 (95% CI, 0.25-0.67) in 2023-2024; for bronchiolitis, the RR was 0.33 (95% CI, 0.15-0.76) in 2022-2023, but the reduction was not significant in 2023-2024 (RR, 0.43 [95% CI, 0.18-1.00]). Conclusions and Relevance: In this cohort of 256 VLRTI cases, the findings suggest that RSV contributed to a broad range of VLRTIs across ages and that RSV Ag-RDT was a useful outpatient antimicrobial stewardship tool, particularly in bronchiolitis. Combined with universal immunoprophylaxis, widespread Ag-RDT use may improve diagnostic accuracy, resource allocation, and clinical outcomes.