P019 Comparison of newly proposed chronic nonbacterial osteomyelitis classification criteria to previous diagnostic criteria

Abstract

Abstract Background/Aims Chronic nonbacterial osteomyelitis (CNO) is an aseptic autoinflammatory bone disease of unknown etiology. This diagnosis can be delayed due to the non-specific nature of symptoms and normal imaging studies. New classification criteria were proposed in 2022. This study seeks to validate these new classification criteria by comparing them to previous diagnostic criteria in a cohort of known CNO patients. Methods This is a retrospective case-series of pediatric patients diagnosed with CNO (n = 39) between 2012 and 2023 in Virginia, USA. The newly proposed classification criteria (Table 1) was applied to this cohort. The entry criteria of chronic bone pain, age <18 years, abnormal radiograph and/or MRI were used prior to applying the newly proposed classification criteria. The 2008 Jansson diagnostic criteria and 2016 Bristol diagnostic criteria were also applied to the cohort for comparison and further validation. The clinical manifestations, laboratory results, and imaging studies that lead to a diagnosis of CNO were reviewed. Results The average age of diagnosis was 10 (range 2-17) years-old with the average time between onset of symptoms to confirmed clinical diagnosis being 24 (range 1-120) months. The most common presenting symptoms were bone pain (100%) and arthritis (49%). Evidence of radiographic abnormalities leading to CNO diagnosis was found with regional MRI (64%), bone scan (44%) with some requiring full body MRI (31%). Only one patient did not meet the new classification criteria (1/39; 3%) because of age <3 years, fever and elevated ESR which together gave less than the required 55 points for criteria fulfillment. One different patient (1/39; 3%) did not meet both the Bristol and Jansson criteria because of unifocal disease and lack of bone biopsy. Conclusion This retrospective chart review validates the newly proposed classification criteria for CNO. Older diagnostic criteria (Jansson and Bristol) both require advanced imaging and at times bone biopsy for fulfillment. We conclude that the newly proposed criteria is easy to apply even in the absence of a bone biopsy or advanced imaging studies. The newly proposed criteria will aid in the development of a homogeneous cohort for future studies about CNO. Disclosure A.M. Patel: Member of speakers’ bureau; ABBVIE, AMGEN, SANOFI. K.S. Lee: None. A.J. Kim: None.