The knee joint in early juvenile idiopathic arthritis - An ROC study for evaluating the diagnostic accuracy of contrast-enhanced MR imaging

Purpose. Diagnosis of juvenile idiopathic arthritis (JIA) remains difficult due to unspecific clinical and laboratory findings, especially in early st ages of the disease. The purpose of our study was to determine the sensitiv ity and specificity of MR imaging in diagnosing JIA of the knee joints. Material and Methods: Forty children (3-17 years old) clinically diagnosed with JIA (follow-up >1 year) of a knee joint and a control group of 40 chil dren with painful knee joints (MR diagnosis: bone bruise of the knee (n=7), normal knee joint (n=12), osteomyelitis (n=6), septic arthritis (n=2), bon e tumor (n= 7) and miscellaneous bone lesions (n=6)) were examined using a 1.5 T MR unit. T1-weighted spin-echo (SE), T2-weighted fast SE, contrast-en hanced T1-weighted SE and 2D gradient echo sequences were performed. The re ceiver operating characteristic (ROC) curves evaluation was conducted by 5 independent radiologists. Results. The positive criteria for diagnosing JIA were joint effusions (n= 40), contrast-enhancing synovitis (n=39), cartilage lesions (n=15), subchon dral erosions and bony destruction (n=1). Sensitivity and specificity were 93.5% and 92.5%, respectively. Both cases of septic arthritis were misdiagn osed as JIA by all radiologists. Conclusion. Contrast-enhanced MR imaging seems to be a highly sensitive too l in establishing the diagnosis of JIA.