[Positron emission tomography with (18)F-FDG in the evaluation of patients with rheumatoid arthritis--a systematic review].

INTRODUCTION Rheumatoid arthritis (RA) is a disease characterized by inflammation of the synovial membrane. Several authors have investigated the role of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose ((18)F-FDG) in RA. OBJECTIVES To systematically review the current literature on the role of (18)F-FDG PET in the diagnosis, determination of disease activity and assessment of treatment response in patients with RA. METHODS Searches were conducted in Medline, Cochrane Library, Lilacs, Pubmed and Scopus in Portuguese, English and Spanish languages, using the keywords "rheumatoid arthritis", "synovitis", "FDG", "PET", "glycolytic metabolism" and "disease activity". RESULTS 142o articles were initially identified, of which only 40 were related directly to the subject. Twelve original articles and three case reports that met the inclusion criteria were selected. DISCUSSION The presence of activated macrophages and fibroblasts in pannus are responsible for the intense periarticular uptake of (18)F-FDG. The uptake patterns do not allow the differential diagnosis with other arthritides. The uptake intensity and the number of joints involved are metabolic parameters of disease activity that correlate well with the composite indices. Longitudinal studies of PET have proven useful in assessing the response to treatment with anti-TNF. When performed early, PET can predict the therapeutic response. CONCLUSION Although the actual role of this new technique for the investigation of RA is not yet established, (18)F-FDG PET is a promising tool in determining the activity and prediction of response to treatment of patients with RA.