Calculate the AST to ALT ratio (De Ritis ratio) and R factor for liver disease pattern analysis. Differential diagnosis tables for alcoholic, viral, and metabolic liver disease.
The AST:ALT Ratio Calculator (De Ritis Ratio) analyzes the relationship between your liver enzymes to help differentiate liver disease etiologies. First described by Fernando De Ritis in 1957, this ratio remains one of the most useful bedside tools for interpreting abnormal liver function tests.
The ratio of AST to ALT provides critical diagnostic information because these enzymes are distributed differently in the liver and have different half-lives. ALT is more liver-specific and predominates in hepatocellular injury, while AST is also found in muscle, heart, kidney, and red blood cells. An AST:ALT ratio above 2 with AST under 300 is one of the most reliable non-invasive markers for alcoholic liver disease. As liver fibrosis progresses to cirrhosis, the ratio typically rises above 1 regardless of etiology, reflecting decreased ALT synthesis by the failing liver.
This calculator also computes the R factor (ratio of ALT elevation to ALP elevation), which distinguishes hepatocellular from cholestatic injury patterns — essential for the initial workup of abnormal liver tests. Together with GGT and clinical context, these ratios narrow the differential diagnosis significantly before any imaging or biopsy.
The AST:ALT ratio is one of the simplest yet most informative calculations from routine blood work. It helps clinicians and patients understand which type of liver disease is most likely, prioritize further testing, and monitor disease progression. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation.
De Ritis Ratio = AST / ALT R Factor = (ALT / ALT ULN) / (ALP / ALP ULN) R >5 → Hepatocellular pattern R 2-5 → Mixed pattern R <2 → Cholestatic pattern De Ritis <1 → Viral/metabolic hepatitis De Ritis 1-2 → Fibrosis/cirrhosis progression De Ritis >2 → Alcoholic liver disease De Ritis >3 → Highly suggestive alcoholic etiology
Result: AST:ALT = 0.80 (Normal pattern). R Factor = 3.5 (Hepatocellular). ALT = 2.5× ULN (Mild elevation).
An AST:ALT ratio of 0.80 (less than 1) is typical of viral hepatitis, MASLD, or drug-induced liver injury. The R factor of 3.5 confirms a hepatocellular injury pattern. Normal GGT makes alcohol unlikely.
Fernando De Ritis first described the AST:ALT ratio in 1957 while studying viral hepatitis. Since then, it has become one of the most widely used liver enzyme ratios in clinical medicine. Its enduring value lies in its simplicity: no special tests, no calculations beyond simple division, and applicability across all liver disease etiologies.
The R factor was formalized by the Council for International Organizations of Medical Sciences (CIOMS) for classifying drug-induced liver injury (DILI). It separates liver injury into hepatocellular (predominantly transaminase elevation), cholestatic (predominantly ALP elevation), and mixed patterns. This classification directs the entire workup: hepatocellular injury warrants viral serologies and autoimmune markers, while cholestatic patterns require imaging for biliary obstruction.
Beyond etiology, the De Ritis ratio has been integrated into composite fibrosis scores. A ratio consistently above 1 in chronic hepatitis C is an independent predictor of advanced fibrosis. The ratio is incorporated into the AAR (AST-ALT ratio) score and contributes to other non-invasive fibrosis assessments alongside platelet count and albumin.
A ratio above 2 (especially 2-3) with AST under 300 U/L is highly suggestive of alcoholic liver disease. This is because alcohol directly injures mitochondria (where AST is concentrated) while ALT is cytoplasmic. Additionally, alcohol depletes pyridoxal phosphate (vitamin B6), which is needed for ALT synthesis.
Yes. In viral hepatitis and MASLD, the ratio is typically below 1 early on (ALT > AST). As fibrosis advances to cirrhosis, the ratio rises above 1 because the cirrhotic liver produces less ALT. A rising ratio over time may indicate disease progression.
The R factor (also called R value) classifies liver injury as hepatocellular (R >5), cholestatic (R <2), or mixed (R 2-5). It is calculated as (ALT/ULN) ÷ (ALP/ULN) and is the first step in the DILI (drug-induced liver injury) assessment algorithm.
Yes. AST is also found in skeletal muscle, heart, and red blood cells. Rhabdomyolysis, myocardial infarction, and hemolysis can dramatically elevate AST relative to ALT. Always check CK to rule out muscle injury if AST is disproportionately high.
GGT (gamma-glutamyl transferase) is elevated in biliary disease and alcohol use. An elevated GGT combined with AST:ALT >2 strongly suggests alcoholic liver disease. Elevated GGT with elevated ALP suggests biliary obstruction. Isolated GGT elevation has many causes (medications, obesity, enzyme induction).
Massive elevations (ALT >1000) are typically caused by acute viral hepatitis, ischemic hepatitis (shock liver), drug/toxin injury (acetaminophen), or acute biliary obstruction. Alcoholic hepatitis alone rarely causes AST above 300.