R-Factor (Drug-Induced Liver Injury Pattern)
Compute the R-factor (Benichou / CIOMS 1990) for suspected drug-induced liver injury: R = (ALT / ALT upper limit) divided by (alkaline phosphatase / ALP upper limit).
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- ALT
- 500 U/L
- ALT upper-normal limit
- 40 U/L
- ALP
- 100 U/L
- ALP upper-normal limit
- 120 U/L
Result: Hepatocellular pattern (R = 15).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- >5
- Hepatocellular pattern of liver injury.
- 2-5
- Mixed pattern of liver injury.
- <2
- Cholestatic pattern of liver injury.
What you enter
- ALT
- ALT upper-normal limit
- ALP
- ALP upper-normal limit
What this is
Sophie Well classifies the result as hepatocellular (R > 5), cholestatic (R < 2), or mixed (R between 2 and 5), which determines the differential and the urgency of stopping the suspect agent.
When to use it
Use this as soon as new liver enzyme elevations show up in a patient on any drug, supplement, or herbal product. The pattern guides workup - hepatocellular injury raises the spectre of acetaminophen, isoniazid, or autoimmune hepatitis; cholestatic injury points at amoxicillin-clavulanate, anabolic steroids, or biliary obstruction. R should be calculated at the time of recognition and re-checked if the pattern shifts; CIOMS is a classification tool, not a causality score (RUCAM does that).
How this is calculated
Benichou C. CIOMS classification. J Hepatol 1990;11:272-276. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.