Systematic review: acute liver failure - one disease, more than 40 definitions.

BACKGROUND: Acute liver failure (ALF) is a clinical syndrome with very high mortality estimates ranging between 60% and 80%. AIM: To investigate the explicitness and extent of variability in the used ALF definitions in the ALF prognostic literature.
METHODS: All studies that pertain to the prognosis of patients with ALF were electronically searched in MEDLINE (1950-2012) and EMBASE (1950-2012). Identified titles and abstracts were independently screened by three reviewers to determine eligibility for additional review. We included English articles that reported original data from clinical trials or observational studies on ALF patients.
RESULTS: A total of 103 studies were included. Of these studies 87 used 41 different ALF definitions and the remaining 16 studies did not report any explicit ALF definition. Four components underlying ALF definitions accounted for the differences: presence and/or grading of hepatic encephalopathy (HE); the interval between onset of disease and occurrence of HE; presence of coagulopathy and pre-existing liver disease.
CONCLUSIONS: The diversity in acute liver failure definitions hinders comparability and quantitative analysis among studies. There is room for improvement in the reporting of acute liver failure definitions in prognostic studies. The result of this review may be useful as a starting point to create a uniform acute liver failure definition.