Value of SPECT/CT in the diagnosis of juvenile idiopathic arthritis in young children: a retrospective case-control study.

OBJECTIVES: Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in childhood, with early diagnosis remaining challenging due to its heterogeneous manifestations and complex pathogenesis. Nuclear medicine imaging, like single photon emission computed tomography (SPECT), which has proven valuable in quantifying inflammation and monitoring disease activity in adult rheumatoid arthritis (RA), may also have diagnostic potential in JIA, given the similarities in synovitis and joint damage between JIA and RA. METHOD: This retrospective case-control study included 29 JIA patients (aged 1-13 years) and 55 non-JIA controls (aged 1-16 years), all undergoing 99Tc-MDP SPECT. The standardized uptake ratio (SUR), defined as the brightness score (BS), was calculated for hip, knee, ankle, and wrist joints using the skull as a reference. Mann-Whitney U test and receiver operating characteristic (ROC) curves were used to assess differences in BS and diagnostic performance (AUC, sensitivity, specificity, and Youden's index). RESULTS: JIA patients showed significantly higher median BS in all target joints, with the most significant differences in bilateral wrists (left wrist: median = 3.25, IQR = 1.35, P = 0.02; right wrist: median = 3.26, IQR = 1.5, P = 0.01). ROC analysis revealed limited adjunctive screening value of the wrist (left AUC = 0.780, P = 0.002; right AUC = 0.813, P = 0.000) with relatively high specificity (0.578 and 0.867) and moderate sensitivity (0.857 and 0.571), while the knee and hip had limited value (AUC ≈ 0.6). CONCLUSIONS: SPECT-based wrist brightness scoring is a potential objective imaging tool for JIA diagnosis. No significant diagnostic value was found in the hip, knee, or ankle joints.