Systematic Review: Current Evidence in Non-Alcoholic Fatty Liver Disease Lacks Relevance to Patients with Advanced Fibrosis

OBJECTIVES: Epidemiological data have shown that individuals with advanced fibrosis are at greatest risk of premature morbidity in NAFLD. Individuals included in clinical trials are often highly selected to remove confounding factors but selection can introduce bias and limit external validity. We examined the external validity of trials in non-alcoholic fatty liver disease (NAFLD) by examining characteristics of participants in observational studies (OS) and randomised controlled trials (RCT) in NAFLD.

DESIGN: A systematic review was performed with structured literature searches for relevant OS and RCT using PubMed and Ovid Embase (1948 - 2016). Identified studies were screened for inclusion by the authors and data extracted. Study populations were compared using t-tests to compare means and variances, in each case weighted by the size of individual studies. Dichotomous data were compared by Chi-squared test.

RESULTS: In total 148 studies were included: 67 RCT and 81 OS including data from 44,860 individuals . Fifteen RCT participants differed from individuals in OS with regard to age, BMI, prevalence of DM, and gender (p < 0.001 in each case). The most pronounced differences were seen between RCT participants and patients with advanced fibrosis. Co-morbid conditions prevalent amongst individuals with NAFLD were frequent exclusion criteria in RCT.

CONCLUSIONS: The characteristics of participants in randomised controlled trials differ to those of the wider population of individuals with NAFLD. These differences may reduce the utility of trial data to individuals with NAFLD at greatest risk of death.