Maddrey Discriminant Function Calculator
Calculate the Maddrey discriminant function from prothrombin time and bilirubin, with a cutoff of 32 for severe disease.
What it does
The Maddrey discriminant function is a bedside score for adults with alcoholic hepatitis. It combines the prolongation of prothrombin time with the total bilirubin. The result helps identify severe disease, which is the group in which corticosteroids are most often considered.
Prothrombin time is measured in seconds. The score uses the difference between the patient's value and a control value, not the patient's value alone. The difference is multiplied by 4.6 and added to the bilirubin in milligrams per deciliter. A result of 32 or more is the usual cutoff for severe alcoholic hepatitis.
The cutoff comes from old treatment trials. In those studies, patients with a high discriminant function had short term mortality that was high enough to justify a trial of steroids. Later work added the Lille score to judge whether a patient responds after several days of treatment. The Maddrey function starts the conversation; the Lille score helps decide whether to continue.
The test depends on the control prothrombin time. A control value from a different reagent or a different laboratory can move the score by several points. The bilirubin unit also matters. Most laboratories in the United States report mg/dL, while many other countries report micromol/L. The conversion is 1 mg/dL equals 17.1 micromol/L.
The score is not specific to alcoholic hepatitis. Any cause of acute liver injury can prolong the prothrombin time and raise bilirubin. The diagnosis still depends on the history, the pattern of liver tests, and the exclusion of other causes. A high score in a patient with ischemic hepatitis or acute viral hepatitis does not carry the same meaning.
How to use
- Confirm the clinical diagnosis of alcoholic hepatitis and exclude other causes of acute liver injury.
- Choose the bilirubin unit used by your laboratory. The default is mg/dL, which is common in the United States.
- Enter the patient's prothrombin time in seconds and the control prothrombin time from the same laboratory run.
- Enter the total bilirubin. If the result is in micromol/L, switch to metric and enter that value.
- Calculate the difference between patient and control PT, multiply by 4.6, and add the bilirubin in mg/dL.
- Compare the result with the cutoff of 32. If the value is 32 or more, discuss steroid therapy and transplant assessment with the treating team.
Formula
- Patient PT
- The patient's prothrombin time in seconds.
- Control PT
- The laboratory control prothrombin time in seconds.
- Bilirubin
- Total bilirubin in mg/dL. If reported in micromol/L, divide by 17.1.
- DF
- Discriminant function. A value of 32 or more is severe.
The constant 4.6 converts the prothrombin time difference into the same scale as bilirubin. The formula uses total bilirubin, not direct bilirubin. Do not use the international normalized ratio in place of prothrombin time seconds. The control PT must come from the same laboratory system as the patient value, because different thromboplastins give different times. The cutoff of 32 is a historical threshold and should be applied with the full clinical picture.
Worked example
Example: DF 32.1, severe disease
A patient with alcoholic hepatitis has a prothrombin time of 18 seconds, a control of 12 seconds, and a total bilirubin of 4.5 mg/dL.
- Patient PT minus control PT: 18 - 12 = 6 seconds.
- Multiply the difference by 4.6: 4.6 x 6 = 27.6.
- Add the bilirubin: 27.6 + 4.5 = 32.1.
- The discriminant function is 32.1.
- The cutoff is 32 or more, and 32.1 is above the cutoff.
- The result is in the severe range, so discuss corticosteroids and early transplant assessment.
Reference table
| DF | Interpretation | Typical direction |
|---|---|---|
| Below 32 | Not in the severe range | Supportive care and monitoring |
| 32 or more (worked: 32.1) | Severe alcoholic hepatitis | Discuss steroids and transplant assessment |
| 15.8 | Example of a below cutoff value | Supportive care |
| 46.8 | Example of a clearly severe value | Steroid discussion and close monitoring |
Limits
- The score is not a diagnostic test for alcoholic hepatitis. It can be high in other forms of acute liver injury.
- The control prothrombin time varies by laboratory and reagent, which can change the result.
- The cutoff of 32 comes from older trials and does not by itself prove that steroids will help.
- The score does not measure response to treatment. The Lille score is used after several days of steroids.
Common mistakes
- Using the international normalized ratio instead of the prothrombin time in seconds.
- Forgetting to convert bilirubin from micromol/L to mg/dL before calculating.
- Using a control prothrombin time from a different laboratory or a different reagent.
- Applying the score to a patient without a clinical diagnosis of alcoholic hepatitis.
- Continuing steroids after day 7 without checking the Lille score or the clinical response.
Try it yourself
Quick checks. Answers sit tucked under each question.
Patient PT 20 seconds, control 12 seconds, bilirubin 10 mg/dL. What is the DF and severity?
20 - 12 = 8. 4.6 x 8 = 36.8. 36.8 + 10 = 46.8. The DF is 46.8, which is severe.
Patient PT 15 seconds, control 12 seconds, bilirubin 2 mg/dL. What is the DF and severity?
15 - 12 = 3. 4.6 x 3 = 13.8. 13.8 + 2 = 15.8. The DF is 15.8, which is below the severe cutoff.
Patient PT 18 seconds, control 12 seconds, bilirubin 171 micromol/L. What is the DF and severity?
171 / 17.1 = 10 mg/dL. 18 - 12 = 6. 4.6 x 6 = 27.6. 27.6 + 10 = 37.6. The DF is 37.6, which is severe.
Questions
What is a Maddrey discriminant function of 32?
A value of 32 or more is the usual cutoff for severe alcoholic hepatitis. It is a reason to discuss steroids and transplant assessment.
Why multiply by 4.6?
The constant puts the prothrombin time difference on the same scale as bilirubin so the two components can be added.
Can I use INR instead of PT?
No. The formula uses prothrombin time in seconds and a control value. INR is a different measure and will not give the same result.
How do I convert bilirubin units?
Divide micromol/L by 17.1 to get mg/dL. For example, 171 micromol/L is 10 mg/dL.
Does a score above 32 mean the patient needs steroids?
It means steroids should be discussed. Active infection, gastrointestinal bleeding, kidney failure, and other contraindications can make steroids unsafe.
What is the Lille score?
A score used after several days of steroid treatment to judge response. It helps decide whether to continue or stop steroids.
Sources
- AASLD: steroids, Maddrey discriminant function, and Lille score in alcohol associated hepatitis
- Study of control prothrombin time in the Maddrey discriminant function