Maddrey Discriminant Function Calculator
Estimate the modified Maddrey discriminant function (mDF) from prothrombin time and total bilirubin for alcohol-associated hepatitis severity assessment.
Example workbook is ready.
Inputs
Patient PT in seconds. Use a decimal point, not a comma.
Use the control/reference PT reported by the same laboratory.
Total serum bilirubin in the unit selected below.
Changing units converts the current bilirubin value.
Maddrey's discriminant function
11.2 is below the commonly used severe-disease threshold of 32.
| Calculation step | Meaning | Value |
|---|---|---|
| PT difference | Patient PT – control PT | 2.0 s |
| Weighted PT difference | 4.6 × PT difference | 9.2 |
| Bilirubin contribution | Total bilirubin normalized to mg/dL | 2.0 |
| Maddrey DF | Weighted PT difference + bilirubin | 11.2 |
The mDF is a clinical severity score, not a diagnosis or a stand-alone treatment recommendation. Laboratory context and the patient's overall condition matter.
Maddrey discriminant function score 11.2, below 32.
How to use this Maddrey Discriminant Function calculator
What this calculator does. This tool calculates the modified Maddrey discriminant function (mDF), a historical clinical severity score used in alcohol-associated hepatitis. It combines the patient's prothrombin time, the laboratory's control prothrombin time, and total serum bilirubin. The result is a score rather than a probability. A commonly used severe-disease threshold is 32 or higher, but the score does not diagnose alcohol-associated hepatitis, establish a person's individual prognosis by itself, or decide whether corticosteroids are appropriate. The AASLD explanation of Maddrey DF and treatment context describes how the modified formula and the 32-point threshold entered clinical use.
When to use it
The calculator is most useful when a clinician or learner already has the three required laboratory values and wants to reproduce an mDF calculation, compare the result with the conventional 32-point threshold, check the effect of a different laboratory control PT, or verify a manual calculation. It can also help when bilirubin is reported in µmol/L rather than mg/dL because the unit control converts the value before applying the formula. It is not intended for self-diagnosis or for choosing medication without clinical evaluation.
How to calculate
- The calculator opens with a complete demonstration: Prothrombin time = 14 seconds, Prothrombin time - control = 12 seconds, and Bilirubin level = 2 mg/dL. The first score and a validated example Excel workbook are available immediately.
- Replace Prothrombin time with the patient's measured PT in seconds, then enter the same laboratory's reference value in Prothrombin time - control.
- Enter Bilirubin level and choose Bilirubin unit. If you switch between mg/dL and µmol/L, the calculator converts the current value rather than just changing the label.
- Read Score in the results panel. The formula line and calculation table show the PT difference, its 4.6 weighting, and the bilirubin contribution so the result can be checked manually.
- Choose Download Excel to export the current validated inputs, score, formula components, and notes as a real .xlsx workbook. Reset clears the demonstration values and results; after Reset, Excel export remains unavailable until a complete valid input set is entered again.
Input guide
Prothrombin time is required and is entered in seconds as a positive decimal number, for example 14. The field accepts standard decimal-point notation such as 14 or 14.5; commas, scientific notation, units typed into the field, and nonnumeric text are rejected. A higher patient PT, with the other inputs unchanged, raises mDF because the difference from the control PT becomes larger. Do not substitute INR for PT seconds.
Prothrombin time - control is also required, in seconds, for example 12. It should be the control or reference PT used by the laboratory associated with the patient's result, not an assumed universal normal. Increasing the control PT lowers the calculated PT difference and therefore lowers mDF. This input is especially important because control PT is not perfectly standardized across laboratories.
Bilirubin level is required and represents total serum bilirubin. A realistic demonstration value is 2 mg/dL. The field accepts a nonnegative decimal number in the selected unit. Higher bilirubin directly raises mDF after normalization to mg/dL. Do not mix direct bilirubin with total bilirubin, and do not enter a µmol/L value while mg/dL is selected.
Bilirubin unit is required and offers mg/dL or µmol/L. The calculator uses 17.1 µmol/L per 1 mg/dL for conversion, so 2 mg/dL becomes 34.2 µmol/L. The mDF formula itself uses bilirubin in mg/dL; the unit selector exists only to make laboratory reports in either unit usable without manual conversion.
Output guide
Score is the modified Maddrey discriminant function. It has no physical unit. It is driven by all three laboratory values after bilirubin is normalized to mg/dL. The result can be zero or even negative when patient PT is at or below control PT and bilirubin is low; that is a mathematical outcome of the formula, not a statement that liver disease is absent. A higher score generally reflects a larger PT prolongation and/or higher bilirubin. Contemporary clinical discussions commonly use mDF ≥ 32 as a severe-disease threshold, but treatment decisions should consider contraindications, infection risk, diagnosis, and other prognostic models.
The calculation table includes PT difference (patient PT minus control PT), Weighted PT difference (that difference multiplied by 4.6), Bilirubin contribution (total bilirubin in mg/dL), and Maddrey DF (the sum of the two score components). These rows are exact identities from the same model used for the displayed score and Excel workbook.
Worked example
Using the first-open demonstration, patient PT is 14 seconds, control PT is 12 seconds, and total bilirubin is 2 mg/dL. First subtract the control: 14 – 12 = 2 seconds. Multiply the PT difference by 4.6: 4.6 × 2 = 9.2. Add bilirubin in mg/dL: 9.2 + 2 = 11.2. The calculator therefore opens with a score of 11.2, matching the formula line, breakdown table, header pill, and workbook checkpoints.
Formula, interpretation, and limitations
The modified formula is mDF = 4.6 × (patient PT – control PT) + total bilirubin in mg/dL. The modification accounts for differences in laboratory control PT, which is why the control value should come from the relevant lab rather than a generic number. An American Family Physician review of alcohol-associated hepatitis summarizes validated prognostic scores, cites the original 1978 Maddrey trial, and places mDF alongside other severity tools.
Current hepatology guidance places mDF alongside other prognostic tools rather than treating it as a complete decision rule. The AASLD alcohol-associated liver disease guidance provides the broader diagnostic and treatment framework. A University of Florida hepatology resource also lists the required patient PT, lab control PT, bilirubin, and score fields for the discriminant function used in alcohol-associated hepatitis.
Medical-use note: This calculator is an educational calculation aid. A high or low mDF should be interpreted by a qualified clinician together with the diagnosis, laboratory method, contraindications, infection status, organ function, and other validated prognostic scores.