ABSTRACT Objective To determine whether the joint use of the Pediatric Comorbidity Index (PCI) and the Pediatric Complex Chronic Condition classification version 3 (PCCC) improves prediction of severe outcomes and resource use among children hospitalized with respiratory tract infections. Design Retrospective nationwide cohort study. Setting Acute care hospitals contributing to the nationwide claims database. Patients All children < 15 years admitted to acute care hospitals due to respiratory tract infection between April 2018 and March 2024 ( N = 275,296). Measurements and Main Results Generalized linear models estimated associations of PCI and PCCC scores with severe outcomes—mechanical ventilation, intensive‐care admission, or in‐hospital death—plus length of stay and total costs. Interactions were assessed on additive and multiplicative scales. Stratification by PCI and PCCC scores revealed that the risks of severe conditions increased from 3.7% at PCI 0% to 8.6% at PCI 4 for children with a PCCC score of 0 and from 11.3% to 38.5% among children with a PCCC score of 1. Among those with PCCC ≥ 2, the risk was high at PCI 0 (52.6%) and did not increase monotonically across PCI strata (range 35.8%–52.6%). Interaction analyses revealed negative additive interactions (−27.1% to −58.5%) and sub‐multiplicative interactions (multiplicative index 0.41–0.73), indicating that combined use of PCI and PCCC refines risk stratification beyond either measure alone. Conclusions Our findings suggest that combining the PCI and PCCC scores yields more precise risk stratification and may support more appropriate allocation of healthcare resources for children with varying levels of comorbidity.
Okubo et al. (Sun,) studied this question.