Pos0777 Childhood Chronic Non-Bacterial Osteomyelitis – Proposal for Assessment of Disease Activity Using Composite Scores.

Background: Chronic non-bacterial osteomyelitis (CNO) is an autoinflammatory bone-disease of unknown origin. How to assess disease activity (DA) in CNO is still debated. No commonly accepted criteria exist for inactive disease and remission. So far, DA estimation has been based on patient, physician and radiologist judgement. The pedCNO disease activity score (consisting of patient's global assessment of disease (PGA) or pain (PAP), the childhood health assessment questionnaire (C-HAQ), the physician global assessment of disease activity (PhGA), ESR and MRI imaging defined number of bone lesions) has been described in analogy to the ACR JIA DA score in a large institutional cohort and validated in the German National Pediatric Rheumatologic Database (NPRD) cohort. Recently the international CARRA CNO initiative has proposed a numeric composite disease activity score (CARRA CDAS) based on the PGA and PAP, in addition to the clinically overt number of affected bone lesions. Objectives: Based on the National Pediatric Rheumatologic Database (NPRD), which collects long-term data of children and adolescents with rheumatic diseases, the CNO cohort was analysed for possible DA scores defining active and inactive disease from different perspectives. In addition to the published pedCNO and the CARRA CDAS further numeric composite disease scores were calculated including not only the patient's but also the physician's perspective in addition to MRI imaging data. Methods: Patients with a confirmed CNO diagnosis who were first included in the NPRD between 2015 and 2020, who had a disease duration of 12 months or less at inclusion and who had at least one follow-up visit within the first 4 years of disease were included in the analysis. Numeric composite scores describing CNO disease activity over time from different perspectives (imaging analysed versus clinical lesional number, patient's and/or physician's focus) were calculated and assessed for responsiveness over time and particularly towards estimation of inactive disease. Results: 400 patients were enrolled, 81 succeeded till 4 years of follow-up. The pedCNO up to 90% improvement of variables was calculated (Table 1) suggesting minimal disease activity in 49% of the patients at last follow-up. DA was described using the recently proposed patient centred CARRA CDAS, in addition to the MRI based variants of composite scores. Further combinations of variables including MRI defined lesions (MRI DAS) or the PhGA were calculated accordingly. The composite score consisting of MRI lesion count, PhGA and PGA seems to describe best DA in CNO patients: In the NPRD patient's reporting of pain was prevalent despite unremarkable MRI analysis. This may document a propensity to pain amplification syndrome in CNO and might limit the interpretation of scores including pain measures. Conclusion: In the NPRD different composite scores implementing DA document a favourable and minimal disease activity in the long run. Composite scores including MRI lesional numbers and/or the PhGA seem to be promising tools reflecting DA. Exclusively patient centred scores might have a bias if pain amplification is present.REFERENCES: NIL. Acknowledgements: We are particularly thankful to the patients, who participate in the National Paediatric Rheumatologic Database. Disclosure of Interests: Christiane Reiser Novartis, Galapagos, Pfizer, sobi, Jens Klotsche: None declared, Martina Niewerth: None declared, Nadine Grösch: None declared, Kirsten Minden: None declared, Hermann Girschick: None declared.