The Cardiovascular
ToolsCalculators

R Factor for Liver Injury

Classifies drug-induced liver injury as hepatocellular, cholestatic, or mixed.

R Factor for Liver Injury
ALT
U/L
ALT upper limit of normal (ULN)
U/L
ALP
U/L
ALP upper limit of normal (ULN)
U/L
Complete the fields above to see the result.

When to use

  • Classifying the biochemical pattern of suspected drug-induced or other acute liver injury once ALT and ALP results are available.

Formula

R = (ALT / ALT ULN) / (ALP / ALP ULN). R >=5: hepatocellular; R <=2: cholestatic; 2 < R < 5: mixed.

Pearls and pitfalls

  • Use the first ALT/ALP pair obtained after liver injury is recognised, before values evolve over the course of the injury.
  • The R ratio describes the biochemical pattern only; it does not by itself establish drug causality, for which structured causality tools (e.g., RUCAM) are used.

References

  1. Danan G, Benichou C. Causality assessment of adverse reactions to drugs--I. A novel method based on the conclusions of international consensus meetings: application to drug-induced liver injuries. J Clin Epidemiol. 1993;46(11):1323-1330.