Clinical analysis of our cohort leads us to define NBO as a distinct disease entity with three clinical presentations: acute NBO, chronic recurrent multifocal osteomyelitis or persistent chronic NBO. Diagnostic criteria were proposed to differentiate NBO from diseases with similar clinical presentation.

Diagnostic study, Level II.

Objective. To accurately differentiate nonbacterial osteitis (NBO) from other bone lesions by applying a clinical score through the use of validated diagnostic criteria.Methods. A retrospective study was conducted to assess data on patients from a pediatric clinic and an orthopedic tertiary care clinic, using administrative International Classification of Diseases codes as well as laboratory and department records from 1996 to 2006. Two hundred twenty-four patients older than age 3 years who had either NBO (n ‫؍‬ 102), proven bacterial osteomyelitis (n ‫؍‬ 22), malignant bone tumors (n ‫؍‬ 48), or benign bone tumors (n ‫؍‬ 52) were identified by chart review. Univariate logistic regression was used to determine associations of single risk factors with a diagnosis of NBO, and multivariable logistic regression was used to assess simultaneous risk factor associations with NBO. Conclusion. The proposed scoring system helps to facilitate the diagnostic process in patients with suspected NBO. Use of this system might spare unnecessary invasive diagnostic and therapeutic procedures. Results. NBO was best predicted by a normal blood cell count (odds ratio

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