Accelerated Severity of Illness Score Enhances Prediction of Complicated Acute Hematogenous Osteomyelitis in Children.

BACKGROUND Severity of illness determination for children with acute hematogenous osteomyelitis should be accomplished during the earliest stages of evaluation to guide treatment and establish prognosis. This study objectively defines an outcome of complicated osteomyelitis and explores an illness severity-based model with an improved ability to predict this outcome as soon and accurately as possible, comparing it to existing models. METHODS Children with Staphylococcus aureus acute hematogenous osteomyelitis (n = 438) were retrospectively studied to identify adverse events and predictors of severity. The outcome of complicated osteomyelitis was ultimately defined as the occurrence of any major or at least 3 minor adverse events, which occurred in 52 children. Twenty-four clinical and laboratory predictors were evaluated through univariate and stacked multivariable regression analyses of chronologically distinct groups of variables. Receiver operating characteristic curve analyses were conducted to compare models. RESULTS Accelerated Severity of Illness Score included: triage tachycardia [odds ratio: 10.2 (95% confidence interval: 3.48-32.3], triage tachypnea [6.0 (2.4-15.2)], C-reactive proteininitial ≥17.2 mg/dL [4.5 (1.8-11.8)], white blood cell count band percentageinitial >3.8% [4.6 (2.0-11.0)], hemoglobininitial ≤10.4 g/dL [6.0 (2.6-14.7)], methicillin-resistant S. aureus [3.0 (1.2-8.5)], septic arthritis [4.5 (1.8-12.3)] and platelet nadir [7.2 (2.7-20.4)]. The receiver operating characteristic curve of Accelerated Severity of Illness Score [area under the curve = 0.96 (0.941-0.980)] were superior to those of Modified Severity of Illness Score = 0.903 (0.859-0.947), Acute Score for Complications of Osteomyelitis Risk Evaluation = 0.878 (0.830-0.926) and Chronic Score for Complications of Osteomyelitis Risk Evaluation = 0.858 (0.811-0.904). Successive receiver operating characteristic curve analyses established an exponentially increasing risk of complicated osteomyelitis for children with mild (0/285 or 0%), moderate (4/63 or 6.3%), severe (15/50 or 30.0%) and hyper-severe (33/40 or 82.5%) acute hematogenous osteomyelitis (P<0.0001). CONCLUSIONS This study improves upon previous severity of illness models by identifying early predictors of a rigorously defined outcome of complicated osteomyelitis.