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Maddrey Discriminant Function Calculator

Enter prothrombin time and bilirubin to compute the Maddrey discriminant function.

How it is calculated

DF = 4.6 × (PTpatient − PTcontrol) + bilirubin. Both prothrombin times are in seconds and bilirubin is total bilirubin in mg/dL. The tool also shows the PT difference in seconds. A result of 32 or more is labelled "Severe ≥32", anything lower "Non-severe <32"; the comparison uses the unrounded value, so 31.97 is displayed as 32.0 but still labelled non-severe. If the patient's PT is shorter than the control the difference is negative and the DF can be below zero. Negative inputs return no result. The control PT comes from the laboratory that ran the test, since reference times differ between labs and reagents. This is a reference calculation, not medical advice.

Worked example

Patient PT 22 s, control PT 12 s, bilirubin 10 mg/dL. PT difference = 22 − 12 = 10.0 s. Multiply: 4.6 × 10 = 46. Add bilirubin: 46 + 10 = 56.0. Because 56.0 is above 32, the tool shows Severe (DF ≥ 32).

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Common mistakes

  • Entering bilirubin in µmol/L (for example 171) instead of mg/dL (10); divide by about 17.1 first, otherwise the DF is wildly high.
  • Using the INR instead of prothrombin time in seconds; the formula needs seconds for both patient and control.
  • Using a generic control value such as 12 s when the lab reported its own control or mean normal PT.
  • Entering direct (conjugated) bilirubin; the formula uses total bilirubin.
  • Reading 32.0 on the screen as severe: the label is decided by the unrounded value and may say non-severe.

Sources

About this calculator

The Maddrey Discriminant Function (MDF) gauges the severity of alcoholic hepatitis from two lab values: MDF = 4.6 × (patient's prothrombin time − control prothrombin time, in seconds) + serum bilirubin (mg/dL). It captures both liver synthetic function (via clotting time) and cholestasis (via bilirubin) in a single number.

An MDF of 32 or higher marks “severe” alcoholic hepatitis, associated with a significantly higher short-term mortality risk, and is the traditional threshold hepatologists and gastroenterologists use to decide whether a patient is a candidate for corticosteroid therapy. This tool is for clinical reference only and is not medical advice.

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Comments (1)

  • Editorial team

    The Maddrey score was devised for alcohol-related hepatitis, so it says nothing about other liver conditions, and a result is one input among many for a hepatologist. Use the prothrombin time in seconds from the same lab that reported the control time, never the INR. Students: tell us which units your lab sheet gives for bilirubin so you can convert correctly before entering it.

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