Advanced Diagnostic Tests for Fatty Liver Disease and NASH

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• Liver Enzyme Tests Limitations
• Diagnosing NAFLD and NASH
• Role of Ultrasound Imaging
• MRI Fat Fraction Protocol
• Elastography for Liver Scarring
• Full Transcript

Liver Enzyme Tests Limitations

Dr. Scott Friedman, MD, clarifies that standard liver enzyme tests like ALT and AST are not liver function tests. They are actually liver injury tests. These enzymes are released from liver cells when damage occurs. Dr. Scott Friedman, MD, explains these tests are relatively nonspecific for diagnosing NAFLD or NASH.

Patients can have significant NASH or NAFLD without elevated AST or ALT levels. Conversely, elevated levels can stem from various other liver conditions. These include viral hepatitis, immune disorders, or adverse drug reactions.

Diagnosing NAFLD and NASH

Accurate diagnosis of fatty liver disease requires more than basic blood work. Dr. Scott Friedman, MD, emphasizes the need to exclude other causes of liver injury. This process is crucial when elevated liver enzymes are present. Platelet counts can also indicate underlying liver problems but lack specificity.

Dr. Anton Titov, MD, and Dr. Friedman discuss the necessity for further evaluation. This often involves advanced imaging techniques or even a liver biopsy. The goal is to pinpoint the exact cause of the abnormal test results and confirm a NAFLD or NASH diagnosis.

Role of Ultrasound Imaging

Dr. Scott Friedman, MD, recommends non-invasive imaging as a key diagnostic step. Ultrasound is a common first-line imaging tool. It is excellent for ruling out focal liver lesions and other structural abnormalities.

However, Dr. Scott Friedman, MD, notes that ultrasound is not a reliable test for detecting liver scarring, or fibrosis. Its primary utility in NAFLD is in identifying the presence of fat within the liver. For a more comprehensive assessment, more advanced imaging modalities are required.

MRI Fat Fraction Protocol

For precise quantification of liver fat, Dr. Scott Friedman, MD, highlights the MRI Fat Fraction protocol. This advanced magnetic resonance imaging technique provides a highly accurate measurement of hepatic fat content. It is far superior to ultrasound for quantifying steatosis.

This method allows clinicians to objectively assess the severity of fatty liver disease. It is a critical tool for monitoring disease progression and response to treatment over time.

Elastography for Liver Scarring

Dr. Scott Friedman, MD, details the importance of tests that measure liver stiffness. This stiffness is a direct indicator of fibrosis, or scarring. Transient elastography, commercially known as FibroScan, is a widely used device for this purpose.

Dr. Friedman also discusses MR Elastography, another powerful tool. Both FibroScan and MR Elastography provide a non-invasive assessment of liver fibrosis. These tests help clinicians stage the disease and determine how advanced the NASH might be, guiding treatment decisions effectively.

Full Transcript

Dr. Anton Titov, MD: Let's discuss diagnostic tests to diagnose fatty liver disease. Of course, there are liver enzymes that are used. There are also platelet levels. There are several scores. There is also a notion that over several decades, the upper limit of normal levels for ALT, for example, has risen as a formal upper edge. Does that mean that it just reflects the higher prevalence of the subclinical NAFLD? I read the numbers like 25 ALT was 20 years ago the norm. ALT test hasn't changed, and now it's about 40 as upper limit.

Dr. Scott Friedman, MD: That's a very important point, Anton. First, let me say that AST and ALT, which are conventional liver tests, are actually enzymes contained within liver cells. When the liver is damaged, it releases those enzymes. We can measure that with a standard lab assay.

They're often referred to incorrectly as liver function tests. They're really liver injury tests. The problem is, they're relatively nonspecific. Patients can harbor quite a bit of NASH or NAFLD, and their AST and ALT may not necessarily be elevated.

When AST or ALT is elevated, it's not necessarily only from NAFLD. So we need to exclude other causes, in particular viral hepatitis, or perhaps immune disorders or even drug reactions. That, along with platelets, are indicative of some liver problems, but they're just not specific enough to NASH or NAFLD for us to use them as a diagnostic test.

It does indicate that we need to do further evaluation either with more imaging, possibly with a FibroScan, and perhaps even with liver biopsy to sort out the reason for those elevated tests.

Dr. Anton Titov, MD: So perhaps from a clinical perspective, if fatty liver disease NAFLD is suspected, or if one wants to find out if they have NAFLD or NASH, they should do structural tests such as Transient Elastography or Magnetic Resonance Elastography to ascertain the structure of the liver. They should not just look at the ALT and AST and platelets.

Dr. Scott Friedman, MD: Absolutely. Certainly, non-invasive imaging is always warranted, particularly ultrasound, to make sure there's nothing focal. Ultrasound is not a good test for liver scarring, but it can determine or identify fat.

There are other tests, in particular, MRI Fat fraction protocol, that can more accurately quantify the amount of fat. MR Elastography gives us an indication of whether there might be scarring.

As you mentioned, tests that measure the stiffness of the liver, particularly a test known as transient elastography. The commercial name that's most commonly used is FibroScan. But there are other devices that also measure stiffness that can also indicate whether there's any MAFLD or NASH and how advanced relatively it might be.