Clinical utility of F-18 sodium fluoride PET/CT for estimating disease activity in patients with rheumatoid arthritis

Abstract

Background: The present study aimed to investigate the clinical implication of F-18 sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) for assessing the disease activity of rheumatoid arthritis. Methods: Seventeen patients with rheumatoid arthritis according to the 2010 American College of Rheumatology/European League Against Rheumatism classification criteria were prospectively enrolled. All enrolled patients underwent F-18 NaF PET/CT along with physical examination, blood test, and ultrasonography. On PET/CT images, two quantitative parameters, F-18 NaF uptake of the joint (joint SUV) and joint-to-bone uptake ratio, were measured for each of the 28 joints included in calculating the disease activity score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR). The relationship between PET/CT parameters and clinical factors and the predictive values of PET/CT parameters for joints with synovitis and high disease activity were evaluated. Results: Tender joints (joint SUV, 13.6 +/- 8.4; joint-to-bone uptake ratio, 1.70 +/- 1.02) and both tender and swollen joints (joint SUV, 13.9 +/- 5.4; joint-to-normal bone uptake ratio, 1.81 +/- 0.76) had significantly higher joint SUV and joint-to-bone uptake ratio than joints without synovitis (joint SUV, 6.0 +/- 2.4; joint-to bone uptake ratio, 0.74 +/- 0.31; P<0.001). On correlation analysis, summed joint SUV (P=0.002, correlation coefficient=0.705) and summed joint-to-bone uptake ratio (P<0.001, correlation coefficient=0.861) of 28 joints showed strong positive correlation with DAS28-ESR after adjustment for age and body mass index. Summed joint SUV showed significant positive correlations with ultrasonography findings (grey scale ultrasonography: P=0.047, correlation coefficient =0.468; power Doppler ultrasonography: P=0.045, correlation coefficient =0.507). On the receiver operating characteristic curve analysis, the sensitivity and specificity for predicting synovitis were 83.2% and 92.7%, respectively, for joint SUV and 81.5% and 90.7%, respectively, for joint-to-bone uptake ratio. Moreover, the summation of both PET/CT parameters of 28 joints showed a diagnostic accuracy of 100.0% for predicting high disease activity in rheumatoid arthritis. Conclusions: Summed joint uptake on F-18 NaF PET/CT had a strong positive correlation with DAS28ESR and accurately predicted high disease activity. F-18 NaF PET/CT parameters might be used as an imaging biomarker for disease activity in rheumatoid arthritis. Trial registration: This study was registered at the Clinical Research Information Service of the Korea (CRIS, http://cris.nih.go.kr/cris/en; registry number, KCT0002597; registered November 2017).