A systematic review of the prevalence of mildly abnormal liver function tests and associated health outcomes.

Liver function tests (LFTs) are commonly performed to investigate asymptomatic individuals or those with nonspecific symptoms. Understanding the prevalence of mildly abnormal LFTs in the general population and the prevalence of liver disease following abnormal LFTs has important implications for the planning of care pathways and the provision of healthcare services. A systematic review of the literature on the prevalence of abnormal LFTs in the general population and their respective health outcomes was conducted. A total of 37 studies reporting data on the prevalence of abnormal LFTs (published between 2000 and 2014) were identified from online database searches or were manually selected from article bibliographies. The prevalence of mildly abnormal LFTs, with one or more abnormal constituents in the LFT, was high at 10-21.7%. The prevalence of severe liver disease within cohorts with abnormal LFTs is relatively low (<5%), and a large proportion of abnormal LFTs remains unexplained. Among individuals with unexplained abnormal LFTs, risk factors include obesity and insulin resistance. Common aetiologies for abnormal LFTs were non-alcohol-related fatty liver disease (NAFLD), followed by alcohol use and viral infections. In addition, normal LFTs do not rule out liver disease. The prevalence of abnormal LFTs depends on the definition and population but is likely to be between 10 and 20% in the general population. Abnormal LFTs are associated with a range of health outcomes but are not necessarily strongly diagnostic of severe liver pathology. Important areas of future research include further studies on the prevalence and predictive ability of LFTs in large, population-representative samples.