Effect of weekend admission on mortality associated with severe acute kidney injury in England: A propensity score matched, population-based study

BACKGROUND Increased in-hospital mortality associated with weekend admission has been reported for many acute conditions, but no study has investigated "weekend effect" for acute kidney injury requiring dialysis (AKI-D). METHODS In this large, propensity score matched cohort of AKI-D, we examined the impact of weekend admission and in-centre nephrology services in 53,170 AKI-D admissions between 1st April 2003 and 31st March 2015 using a hospital episode statistic dataset. Propensity score matching (PSM) was performed to match 4284 weekend admissions with AKI-D with 14,788 admissions on weekdays. RESULTS Of the 53,170 admissions with AKI-D in the whole dataset, 12,357 (23%) were at weekends. The unadjusted mortality for weekend admissions was significantly higher compared to admissions on weekdays (40·6% versus 39·6%, p 0·046). However, in multivariable analysis of the PSM cohort, the odds of death for weekend admissions with AKI-D was 1·01 (95%CI 0·93,1·09). Mortality was higher for weekend admissions in West Midlands (odds ratio (OR) 1·32, 95% confidence interval (CI) 1·05, 1·66) and lower in East of England (OR 0·77, 95%CI 0·59, 1·00) but was not different to weekday admissions in all other regions. In 2003-04, weekend admissions had lower odds of death (OR 0·45, 95%CI 0·21, 0·96) and in 2010-11 higher odds of death (OR 1·28, 95%CI 1·00, 1·63) but in the other ten years observed, there was no significant difference in mortality between weekday and weekend admissions. Provision of in-centre nephrology services was associated with lower odds of death at 0·57 (95%CI 0·54, 0·62). CONCLUSIONS Weekend admissions in patients with AKI-D had no effect on mortality. Further research is warranted to elucidate the reasons for the lower mortality in hospitals with in-centre nephrology services.