How do I calculate the MELD score for a 48-year-old woman with chronic heavy alcohol use, elevated alkaline phosphatase, total bilirubin 7.3 mg/dL, and prothrombin time 13.7 seconds?

Calculating the Maddrey Discriminant Function (MDF)

To calculate the MDF for this patient, you need the control prothrombin time (PT), which is missing from your data; the formula is MDF = 4.6 × (Patient PT – Control PT) + Total Bilirubin (mg/dL), so with PT 13.7 seconds and bilirubin 7.3 mg/dL, the MDF will range from approximately 14 to 21 depending on which control PT you use (12,13.5, or 14.8 seconds). 1

The MDF Formula and Required Values

• The modified discriminant function requires three values: patient PT in seconds, control PT in seconds, and total bilirubin in mg/dL 2, 1
• Your patient's values are: PT 13.7 seconds and total bilirubin 7.3 mg/dL 1
• The missing piece is the control PT, which varies by institution and typically ranges from 12 to 14.8 seconds 3

Calculating MDF with Different Control PT Values

Using the formula MDF = 4.6 × (13.7 – Control PT) + 7.3: 1

• If control PT = 12 seconds: MDF = 4.6 × (13.7 – 12) + 7.3 = 4.6 × 1.7 + 7.3 = 15.1 1
• If control PT = 13.5 seconds: MDF = 4.6 × (13.7 – 13.5) + 7.3 = 4.6 × 0.2 + 7.3 = 8.2 1
• If control PT = 14.8 seconds: MDF = 4.6 × (13.7 – 14.8) + 7.3 = 4.6 × (–1.1) + 7.3 = 2.2 1

Clinical Interpretation

• MDF < 32 indicates lower short-term mortality risk (approximately 90% survival at one month) and does not typically warrant corticosteroid therapy 2, 1
• MDF ≥ 32 defines severe alcoholic hepatitis with 30–50% one-month mortality and prompts consideration of corticosteroid therapy 2, 1
• Based on all three possible control PT values, this patient's MDF is well below 32, suggesting non-severe disease by MDF criteria 1

Important Caveats About Control PT Selection

• The choice of control PT significantly impacts whether patients receive steroids (70% qualify with control PT 12 seconds vs. only 52% with control PT 14.8 seconds), but this choice does not impact actual 30-day survival 3
• Your institution's laboratory should provide the control PT value they use for their PT assay 3
• Different laboratories may report different control PT values, creating variability in MDF calculations across institutions 4, 3

Consider Calculating MELD Score Instead

• The MELD score is superior to MDF for predicting 30-day survival in alcoholic hepatitis (AUROC 0.767 vs. 0.735) and does not require a control PT value 3
• MELD formula: 3.8 × log(bilirubin mg/dL) + 11.2 × log(INR) + 9.6 × log(creatinine mg/dL) + 6.4 1
• You need the INR (not just PT in seconds) and serum creatinine to calculate MELD 1
• MELD > 20 is the threshold for considering corticosteroid therapy, equivalent to MDF ≥ 32 1

Practical Recommendation

• Contact your laboratory to obtain the control PT value they use for standardization 3
• Simultaneously obtain INR and creatinine to calculate MELD score, which provides more reliable prognostic information 1, 3
• Calculate both MDF and MELD for comprehensive risk stratification, as guidelines recommend using both scores 1, 5