Potoupni V, Georgiadou M, Chatzigriva E, et al. - The researchers conducted this systematic review and a meta-analysis to compare circulating tumor necrosis factor (TNF)-α levels in patients with histologically confirmed nonalcoholic fatty liver disease (NAFLD) (simple steatosis or nonalcoholic fatty liver and/or nonalcoholic steatohepatitis) and controls. A systematic search was conducted in PubMed, Scopus and the Cochrane Library. Fifty-six studies, published between 2003 and 2019, were eventually involved, with data from 5,848 people (1,634 controls and 4,214 NAFLD patients). TNF-α standardized mean difference was not related to age, BMI and alanine aminotransferase in any pair of comparisons. Circulating TNF-α levels were higher in NAFLD patients than in controls. In addition, higher levels of circulating TNF-α were linked to the severity of NAFLD.