gastroenterology & hepatologyformula

Maddrey Discriminant Function

The Maddrey Discriminant Function assesses severity of alcoholic hepatitis using prothrombin time prolongation and bilirubin. Formula: 4.6 × (patient PT − control PT) + bilirubin (mg/dL). A DF ≥32 defines severe disease and historically guides the decision to initiate corticosteroid therapy.

inputs

seconds
Your lab's normal control PT — typically 12–14 seconds
seconds

✓ when to use

Use in patients with confirmed or suspected alcoholic hepatitis to identify severe disease (DF ≥32) that may benefit from corticosteroid therapy. Should be calculated at presentation and used alongside the Lille score (day 7) to assess steroid response.

✗ when not to use

DF requires the laboratory control PT, which varies between labs. Using INR-based alternatives avoids this issue but changes the threshold. DF does not account for renal function (MELD is better for overall mortality prediction). Not applicable for other causes of hepatitis.

clinical pearls

  • The formula is: DF = 4.6 × (patient PT − control PT) + total bilirubin in mg/dL. If bilirubin is in µmol/L, divide by 17.1 first. The PT difference (not the absolute PT) is used.
  • The control PT is YOUR lab's normal reference PT, not a universal standard. It is usually 12–14 seconds but varies by reagent and analyser. Always check with your lab.
  • If DF ≥32 and steroids are started, reassess at day 7 with the Lille score. Lille >0.45 indicates non-response — stop steroids (continuing them in non-responders adds infection risk without benefit).
  • MELD ≥21 is an alternative severity threshold that some guidelines prefer because it uses INR (standardised) rather than PT (lab-dependent) and includes creatinine. In practice, both are used.
  • Contraindications to corticosteroids in severe alcoholic hepatitis include: active GI bleeding, active infection (including TB), hepatorenal syndrome, and pancreatitis. Screen for infection before starting steroids.

related tools

lilleDay 7 steroid response assessmentmeldAlternative severity assessmentchild-pughOverall cirrhosis staging