What is the prevalence of MRI-detected inflammation and erosions in small joints in the general population? A collation and analysis of published data

INTRODUCTION: MRI sensitively depicts erosions, bone marrow edema (BME) and synovitis in rheumatoid arthritis (RA). Recently developed European League Against Rheumatism (EULAR) recommendations stated that MRI is valuable to improve the certainty of a considered diagnosis and to detect structural damage at an early time point. However, these recommendations were mainly based on the data of patients with RA; prevalences of MRI features in the general population were not extensively explored. We reviewed the literature on MRI studies including symptom-free persons to assess the occurrence of MRI features. METHODS: Medical literature databases up to September 2013 were systematically reviewed for symptom-free persons with MRI data on metacarpophalangeal, wrist and metatarsophalangeal joints. Data were extracted and summarised. When allowed because of comparable scanning and scoring protocols, a mean frequency of features was calculated. RESULTS: Of the 338 articles screened, 31 studies evaluated MRI findings in symptom-free persons (n=516 in total). Both the imaging techniques (<1/≥1 T, with/without contrast enhancement) and the scoring methods (non-validated or RA MRI score (RAMRIS)) varied widely, prohibiting direct comparisons of the results of many studies. 15 studies scored data according to RAMRIS; combining data of similar joint regions showed that erosions (RAMRIS ≥1) were present in 33–52% of symptom-free persons. Similarly, synovitis was present in 27% and BME in 0–16% of symptom-free persons. The prevalence of MRI-detected erosions increased with age. CONCLUSIONS: MRI features, erosions in particular, occur frequently in symptom-free persons. Before MRI can be implemented in the diagnostic process, larger studies should be conducted determining the degree and combination of MRI features that are disease specific.