Reappraisal of bone scintigraphy as a new tool for the evaluation of disease activity in patients with rheumatoid arthritis.

We aimed to compare the reliability of bone scintigraphy (BS) and fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)-derived parameters in the detection of active arthritis in 28-joint areas and evaluate the reliability of joint counts between BS and clinical assessment in patients with rheumatoid arthritis (RA). We enrolled 106 patients (67 in the development group and 39 in the validation groups) with active RA who underwent BS, 18F-FDG PET/computed tomography (CT), and clinical evaluation of disease activity. We compared the results of BS-derived joint assessment with those of PET-derived and clinical joint assessments. Subsequently we developed a disease activity score (DAS) using BS-positive joints and validated it in an independent group. The number of BS-positive joints in 28-joint areas significantly correlated with the swollen /tender joint counts (SJC/TJC) and PET-derived joint counts. A BS uptake score of 2 (strong positive) was significantly more sensitive compared with a BS uptake score of 1 (weak positive) in detecting a PET-positive joint among the 28-joints. After conducting multivariate analyses including erythrocyte sediment rate (ESR) and patient global assessment (PGA) in addition to BS-derived parameters, BS/DAS was obtained as follows: 0.056 × number of BS-positive joints in 28 joints + 0.012 × ESR + 0.030 × PGA. A significant correlation between BS/DAS and DAS28-ESR was confirmed in the validation group. Strong positive uptake of BS is sensitive and reproducible for the detection of active joints, and can complement the clinical assessment of disease activity in RA.

Development and Validation of an 18 F-Fluorodeoxyglucose-Positron Emission Tomography With Computed Tomography-Based Tool for the Evaluation of Joint Counts and Disease Activity in Patients With Rheumatoid Arthritis.

OBJECTIVE: Clinical joint count assessment is important for detecting synovitis but its reliability is a subject of controversy. This study was undertaken to assess the correlation of positron emission tomography (PET)-derived parameters in 68 joints with disease activity and to compare the reliability of joint counts between PET with computed tomography (CT) and clinical assessment in patients with rheumatoid arthritis (RA). METHODS: We enrolled 91 patients with active RA (69 in a development group and 22 in a validation group) who underwent concurrent 18 F-fluorodeoxyglucose (18 F-FDG)-PET-CT and clinical disease activity evaluation. PET-derived parameters were compared with disease activity assessed using clinical joint count parameters. A Disease Activity Score (DAS) using counts of PET-positive joints was developed, and then validation studies were performed in an independent group. RESULTS: The number of PET-positive joints (of 28 and 68 joints) was significantly correlated with the swollen joint count (SJC) and tender joint count (TJC) and the DAS in 28 joints using the erythrocyte sedimentation rate (DAS28-ESR). Intraobserver and interobserver reliability of PET for the affected joint counts were excellent. Interobserver reliability between nuclear medicine physicians and rheumatologists was good for the SJC and TJC in both 28 joints and 68 joints. After multivariate analyses, including ESR and patient's global assessment of disease activity (PtGA) in addition to PET-derived parameters, the PET/DAS was derived as (0.063 × number of PET-positive joints in 28 joints) + (0.011 × ESR) + (0.030 × PtGA). A significant correlation between the PET/DAS and the DAS28-ESR was confirmed in the validation group (P < 0.001). CONCLUSION: PET-CT could serve as a sensitive and reliable method in the evaluation of disease activity in RA patients, and may be applicable as a research tool, particularly in clinical trials.