Age-Stratified Epidemiology of Respiratory Pathogens and the Value of Customizable Syndromic Testing Using the LIAISON PLEX Respiratory Flex Assay.

Molecular syndromic assays have improved respiratory diagnostics by enabling the simultaneous detection of multiple pathogens from a single sample. However, fixed-panel designs may not align with age-specific prevalence patterns or evolving epidemiologic trends, limiting clinical utility and reimbursement viability. In this study, 1520 positive nasopharyngeal swabs from symptomatic individuals collected during the 2022 to 2023 respiratory season were analyzed by using the LIAISON PLEX Respiratory Flex Assay to evaluate the benefits of customizable, tiered testing strategies. Diagnostic yields from a standard-of-care panel were compared with tiered (core-plus-reflex) frameworks across pediatric (age ≤21 years), adult (age 22 to 64 years), and elderly (age ≥65 years) cohorts. Weighted analyses revealed that 99.8% of cases were viral, while bacterial pathogens accounted for <1%. The most commonly detected viruses included severe acute respiratory syndrome coronavirus 2 (28.2%), human enterovirus/rhinovirus (17.1%), influenza A (11.9%), and human coronavirus (7.4%). Age-related differences were observed, with human enterovirus/rhinovirus and adenovirus more common in pediatric patients, whereas severe acute respiratory syndrome coronavirus 2 and influenza A predominated in adults and the elderly. Standard-of-care panels captured only 58% of infections overall and 33% in pediatric patients; the tiered testing approach identified ≥99% of infections using flexible core-plus-reflex panels. Moreover, core panel targets alone accounted for >76% of all detections. These findings underscore the diagnostic, clinical, operational, and cost management value of age-informed, customizable testing frameworks to improve detection, reduce unnecessary testing, and support stewardship.