- The definitive diagnostic procedure for confirming non-alcoholic steatohepatitis (NASH) in patients with diabetes is the liver biopsy.
- This is because NASH is characterized not only by fat accumulation in the liver but also by inflammation and hepatocellular injury, which cannot be reliably distinguished by non-invasive tests alone.

- While techniques like ultrasound elastography and magnetic resonance imaging proton density fat fraction (MRI-PDFF) are useful in detecting liver fat and assessing fibrosis, they cannot definitively identify the presence of inflammation and cellular damage that define NASH.

- Serum alanine aminotransferase (ALT) levels may be elevated in NASH, but they are not specific and can be normal in many cases, thus lacking diagnostic precision.

- In summary, liver biopsy remains the gold standard for diagnosing NASH because it allows for direct histological evaluation of steatosis, inflammation, ballooning degeneration, and fibrosis.

Reference: Harrison’s Principles of Internal Medicine, 20th Edition, Chapter on Liver Disease, Page 2879