Validation and Modification of a Severity of Illness Score for Children With Acute Hematogenous Osteomyelitis

Background: Children with osteomyelitis demonstrate a wide spectrum of illness. Objective measurement of severity is important to guide resource allocation and treatment decisions, particularly for children with advanced illness. The purpose of this study is to validate and improve a previously published severity of illness scoring system for children with acute hematogenous osteomyelitis (AHO). Methods: Children with AHO were prospectively studied during evaluation and treatment by a multidisciplinary team who provided care according to evidence-based guidelines to reduce variation. A severity of illness score was calculated for each child and correlated with surrogate measures of severity. Univariate analysis was used to assess the significance of each parameter within the scoring model along with new parameters, which were evaluated to improve the model. The scoring system was then modified by the addition of band count to replace respiratory rate. The modified score was calculated and applied to the prospective cohort followed by correlation with the surrogate measures of severity. Results: One hundred forty-eight children with AHO were consecutively studied. The original severity of illness score correlated well with length of stay and other established measures of severity. Band percent of the white blood cell differential >= 1.5% was found to be significantly associated with severity and chosen to replace respiratory rate in the model. The modified calculated severity scores correlated well with the chosen surrogate measures and significantly differentiated children with osteomyelitis on the basis of causative organism, length of stay, intensive care, surgeries, bacteremia, and disseminated or multifocal disease. Conclusions: The findings of this study validate the previously published severity of illness scoring tool in large cohort of children who were prospectively evaluated. The replacement of respiratory rate with band count improved the scoring system.