Chen YF, et al. - A systematic review and meta-analysis on 68 studies covering over 640 million admissions were carried out by the contributors to determine the differences in patient outcomes between weekend and weekday hospital admissions, and factors influencing known as the weekend effect. Based on the grading of recommendations, assessment, development, and evaluations framework, for concluding weekend/weekday difference in hospital care quality from the observed weekend effect, the overall quality of evidence was graded as ‘very low'. To be a reliable indicator of care quality at weekends, a single cause of the weekend effect was uncertain.