Maddrey’s Discriminant Function Calculator

Written by Great Medico

Updated September 24, 2026 •2 min read

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One liver score rarely tells the whole story, but the arithmetic can still be useful when its scope is clear. Maddrey’s Discriminant Function Calculator applies the named formula to the entered clinical variables and keeps the limitations visible.

What this calculator does

Maddrey’s Discriminant Function Calculator uses Patient PT, Control PT, and Serum bilirubin to produce the maddrey discriminant function used by this calculator. It only uses the fields shown in this calculator; it does not silently add tests, diagnoses, symptoms, or clinical variables that are absent from the interface. Uses standard health-calculator relationships where a stable equation exists; complex or policy-dependent tools expose assumptions/points so the result can be checked against the current clinical or public-health source.

How to use it

Enter or select Patient PT, Control PT, and Serum bilirubin. Keep laboratory units consistent and use values from the clinical time point required by the named model. If an input is unknown, it is better to leave the calculation unresolved than to invent a value.

How the calculation works

Maddrey’s discriminant function = 4.6 × (patient prothrombin time − control prothrombin time) + serum bilirubin in mg/dL.

Example

Using the calculator’s prefilled demonstration values, the primary output is 44.8, labeled “Maddrey discriminant function”; PT prolongation is 8 s. That sample is useful for checking the calculation path, but real interpretation should use verified measurements from the same clinical or study context.

How to interpret the result

Read maddrey discriminant function as the result of the named liver/GI model. Use it for the population and purpose in which the model was validated, and avoid interpreting the number as a stand-alone diagnosis, prognosis, or treatment indication.

Limitations and notes

Cutoffs can differ by disease population and guideline, and lab values can change quickly with treatment or acute illness. Use trends, the correct indication, and confirmatory testing or specialist assessment when the result could change management.