Background/Purpose: A challenge in the management of Juvenile Idiopathic Arthritis (JIA) is most of the core set of assessment measurements are subjective by nature.  A validated, accessible, objective tool that can evaluate disease response is lacking.  Musculoskeletal Ultrasound (MSUS) is a non-invasive, efficient, well accepted imaging tool capable of being used at the bedside by a trained ultrasonographer for the assessment of inflammatory arthritis. MSUS is known to have better sensitivity and reliability to detect synovitis than clinical examination.  The aims of this study are 1. Develop and assess reliability of a comprehensive pediatric MSUS scoring system; 2. Determine the minimum number of joints needed to assess MSUS-evidenced disease activity in JIA; 3. Evaluate feasibility and acceptability from both patient/parent and clinician experience of a limited MSUS.

Methods: JIA patients presenting with an active joint count >4 without recent intraarticular corticosteroid injection in the past month, able to perform first visit within 1 week of starting a Disease-modifying Antirheumatic Drug were eligible for this study. General demographic and clinical data, a comprehensive clinical physical examination and a 44 joint MSUS examination by an American College of Rheumatology Musculoskeletal Ultrasound certified pediatric rheumatologist was performed at baseline. Gray-scale B mode and power Doppler images were obtained for each view. Authors developed an Image Acquisition and Image Scoring Manual.  Calibration exercises to assure reliability amongst scorers were performed prior to the actual scoring process for the study. Determination of a limited joint examination was made by a data reduction process to detect at least 90% synovitis within the comprehensive exam. To assess inter-rater agreement of scoring between raters, intraclass correlation coefficient (ICC) with a 95% confidence interval was used.

Results: For a 44 joints MSUS examination a total of 248 US views per patient were identified. Three calibration exercises addressing scoring reliability were necessary to establish an excellent inter-rater agreement (ICC = 0.76-0.85) for all joints but for the shoulder (ICC = 0.49, fair agreement), therefore all shoulder joints images were scored by all raters. A total of 31 patients were enrolled (10 males and 21 females). A preliminary analysis in 15 subjects reveals that 60% of patients have polyarticular RF-negative JIA with a median time from arthritis symptom onset to study visit of 25 months (range 5- 49 months). Patient mean age is 14 years of age (range 10-16 years). Average time of completion was 155 min with 90% retention.  By MSUS, the most common joints involved were wrist (87%), knee (80%), ankle (73%), elbow (73%), MCP 3 (53.3%) as well as MTP 1 (53.3%). Initial data suggest that US examination of bilateral elbow, ankle, knee and/or wrist joints has a 100% sensitivity to capture synovitis within the comprehensive US examination.

Conclusion: A limited MSUS examination will help determine the role of MSUS as a diagnostic and prognostic instrument in pediatrics. It will improve clinical assessment of disease activity in JIA and strengthen medical decision making.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/musculoskeletal-ultrasound-study-in-childhood-arthritis-a-limited-examination/