AST:ALT Ratio (De Ritis Ratio)

What is the AST:ALT ratio?

AST (aspartate aminotransferase, also called SGOT) and ALT (alanine aminotransferase, also called SGPT) are liver enzymes measured in every liver function test. While both rise when liver cells are damaged, they rise to different degrees depending on the cause. The AST:ALT ratio, also called the De Ritis ratio, is calculated by dividing the AST value by the ALT value. The pattern of which enzyme rises more provides a diagnostic clue to the underlying cause of liver damage.

AST:ALT ratio interpretation

Why is AST:ALT >2 typical of alcoholic liver disease?

In alcoholic liver disease, alcohol and its metabolite acetaldehyde directly damage mitochondria (where AST is concentrated in liver cells), causing disproportionate AST release. Simultaneously, alcohol depletes pyridoxal-5-phosphate (vitamin B6), which is required for ALT synthesis: so ALT levels are relatively suppressed. This two-part mechanism explains why AST rises more than ALT in alcoholic liver injury.

Why is ALT higher than AST in viral hepatitis and fatty liver?

In viral hepatitis and NAFLD, hepatocyte cell membrane damage is the primary mechanism, and ALT is predominantly cytoplasmic (released easily through the damaged membrane). ALT is also more specific to the liver than AST (which also comes from heart, muscle and other tissues). So in non-alcoholic liver disease, ALT is the more sensitive and more elevated marker.

Other tests to interpret alongside the ratio

Questions to ask your doctor

• What is likely causing my liver enzyme elevation?
• Do I need a hepatitis B and C test?
• Should I have a liver ultrasound?
• Is alcohol use contributing to my liver results?
• Do I need a liver biopsy?

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Liver Function Tests. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK482489
2. Hepatic Cirrhosis. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK482419

References

Sources cited on this page. PubMed links open the original abstract.

1. Dufour DR, Lott JA, Nolte FS, Gretch DR, Koff RS, Seeff LB. Diagnosis and monitoring of hepatic injury. I. Performance characteristics of laboratory tests. Clin Chem. 2000;46(12):2027–2049. PMID 11114556 · doi:10.1093/clinchem/46.12.2027

What ALT and AST each measure

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are intracellular enzymes that leak into the bloodstream when liver cells (hepatocytes) are damaged. They are the primary markers of hepatocellular (liver cell) injury – distinct from biliary markers (ALP, GGT) and synthetic function markers (albumin, INR).

• ALT (alanine aminotransferase): Found predominantly in the liver. Highly liver-specific – a raised ALT almost always indicates liver cell injury. Normal range: approximately 7–40 IU/L (laboratory-dependent).
• AST (aspartate aminotransferase): Found in liver, cardiac muscle, skeletal muscle, kidney, and red blood cells. Less liver-specific than ALT – raised AST without raised ALT is often from muscle rather than liver. Normal range: approximately 10–40 IU/L.

Both enzymes are released in proportion to the degree of hepatocyte death – enzyme levels in the thousands indicate massive liver necrosis (as in paracetamol overdose or ischaemic hepatitis); levels in the tens to low hundreds are typical of chronic hepatitis or NAFLD.

The AST:ALT ratio – a diagnostic clue

The ratio of AST to ALT (De Ritis ratio) provides an important clinical signal:

• AST:ALT below 1 (ALT predominates): Typical of viral hepatitis (hepatitis B and C), non-alcoholic fatty liver disease (NAFLD), and drug-induced liver injury. The liver is damaged but alcohol is not the cause.
• AST:ALT ratio 1–2: Overlapping causes – could be alcohol, NASH, or other hepatocellular injury.
• AST:ALT above 2 (often above 3): Strongly suggests alcoholic liver disease (alcoholic hepatitis). The mechanism: alcohol depletes pyridoxal phosphate (vitamin B6 – an ALT cofactor) and simultaneously upregulates AST synthesis. This biochemical footprint is sufficiently specific that an AST:ALT ratio above 2 in a person with heavy alcohol use is often treated as diagnostic of alcoholic hepatitis without liver biopsy.
• AST:ALT above 3 with very elevated AST, normal or mildly elevated ALT: Consider rhabdomyolysis (muscle breakdown releasing AST into blood) or cardiac muscle injury (myocardial infarction – cardiac troponin is the preferred test but AST was historically used before troponin was available).

Degree of elevation and what it implies

The magnitude of ALT/AST elevation correlates with acuity and severity of liver injury:

• Mild elevation (1–3× upper limit of normal): Non-specific; found in NAFLD, medications, thyroid disease, coeliac disease, vigorous exercise
• Moderate elevation (3–10× ULN): Significant hepatocellular injury – viral hepatitis, alcoholic hepatitis, drug toxicity
• Severe elevation (above 10× ULN): Acute liver injury – paracetamol overdose, ischaemic hepatitis, autoimmune hepatitis, acute viral hepatitis
• Massively elevated (above 100× ULN – ALT in thousands): Acute liver necrosis – typically paracetamol overdose, ischaemic hepatitis, Budd-Chiari syndrome (hepatic vein thrombosis)