Emerging Trends in the Diagnosis of Non-Alcoholic Fatty Liver Disease
September 22, 2017 - MCI Canada
Non-alcoholic fatty liver disease (NAFLD) is an umbrella term for a variety of illnesses, from simple steatosis to non-alcoholic steatohepatitis (NASH) through to advanced fibrosis and cirrhosis. The most common of all chronic liver diseases, NAFLD affects one in every three people.
NAFLD occurs when more than five percent of hepatocytes are steatotic in patients who do not consume excessive amounts of alcohol. Although usually benign, NAFLD progresses to more serious complications for approximately 30 percent of affected patients and is a major cause of liver transplantation. As well, the presence of NAFLD increases the risk of heart disease and death and doubles the risk for type II diabetes, independent of the severity of liver injury.
Diagnosis of NAFLD Supported with New Techniques
Many people affected by NAFLD remain undiagnosed. Screening is not required for the general population, and diagnosis usually occurs only after incidental discoveries of rising liver enzyme levels or when steatosis appears on imaging (such as during an ultrasound).
As affected patients are often asymptomatic, recognizing patients with at-risk characteristics is an important first step in the diagnosis process. Liver biopsy remains the gold standard for diagnosing and staging NAFLD, but most patients can be accurately diagnosed via non-invasive tests. No single lab test can diagnose NAFLD, but a variety of tools and methods, including blood tests and imaging, can contribute to an accurate diagnosis. Throughout this spectrum of NAFLD diagnostic methods, new trends are emerging that are making diagnosis easier and more effective.
Liver Biopsy Aids New Staging System
Although often not required for diagnosis, liver biopsy is the definitive test for NAFLD. The test also assesses hepatic steatosis, hepatocellular injury, fibrosis, and inflammation. Using this information, the recently introduced SAF score (assessing steatosis (S), activity (A), and fibrosis (F)) is proving more accurate than the more common NAFLD Activity Score (NAS) staging system.
The invasive nature of a liver biopsy often complicates the decision to use it as a diagnostic measure. Typically, a biopsy should only be used after non-invasive procedures prove indeterminate.
Advances in Non-Invasive NAFLD Diagnostic Techniques
Several non-invasive diagnostic techniques have been studied to subcategorize NAFLD patients and assist in management decisions. The ideal non-invasive test has not yet been found, which helps to explain the multitude of tests available. New diagnostic biomarkers and complex models to predict steatosis, NASH, and fibrosis have been proposed, and a study in patients with morbid obesity found that non-invasive biomarkers provided an accurate prediction of advanced fibrosis. As well, a commercially available combination of serologic markers has been found to have a moderate sensitivity and high specificity for determining advanced fibrosis.
Once suspected through blood tests and clinical features, fatty infiltration of the liver can be confirmed with imaging. The constant development of magnetic resonance imaging (MRI) technology is improving accurate diagnosis of markers that cause NAFLD. Ultrasonography and ultrasound are also widely used to assess hepatic steatosis, but ultrasounds cannot reliably detect mild steatosis.
A new ultrasound technique called Controlled Attenuation Parameter (CAP) measures steatosis together with liver stiffness using transient elastography (TE) and will likely see more clinical use in coming years. In its largest study, CAP accurately detected steatosis for mild, moderate, and severe steatosis independent of comorbidities. However, diagnostic thresholds have not yet been clearly identified for NAFLD.
Emerging Non-Invasive Trends
New diagnostic markers and non-invasive methods of diagnosing NAFLD have recently been discovered, and the continuous improvement of MRI, TE, and CAP imaging techniques provide new options for NAFLD diagnosis. Although growing in reliability and accuracy, non-invasive, tests do not currently replace the certainty of a liver biopsy diagnosis. However, they may help patients with either very low or very high risk of advanced cirrhosis or fibrosis avoid the need for biopsy in some cases.
Currently, there are no approved treatments for NAFLD or NASH, except lifestyle modifications. Emerging trends in the diagnosis of non-alcoholic fatty liver disease can help us gain a better sense of the burden NAFLD poses on both the individual and society, and ensure that patients make necessary changes as early as possible to diminish the effects of the disease.
Want to learn more about emerging technologies in the diagnosis of NAFLD? Attend GHS 2018 to stay up-to-date on groundbreaking diagnostic trends.
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