Carithers Dosage Calculator

Carithers Index (Maddrey DF) Calculator

Calculate Alcoholic Hepatitis Severity and Steroid Dosage Requirements

Results

Understanding the Carithers Index (Maddrey Discriminant Function)

The Carithers Index, more commonly known as the Maddrey Discriminant Function (mDF), is the gold standard clinical tool used by gastroenterologists and hepatologists to evaluate the severity of alcoholic hepatitis. Developed through the landmark research of Dr. Carithers in 1989, this mathematical formula helps clinicians identify patients at high risk of short-term mortality who may benefit from corticosteroid therapy.

The Mathematical Formula

The calculation relies on two critical laboratory parameters: the Prothrombin Time (PT), which measures blood clotting efficiency, and Serum Bilirubin levels. The formula is as follows:

DF = 4.6 × [Patient PT (sec) – Control PT (sec)] + Serum Bilirubin (mg/dL)

Interpreting the Results

  • DF Score < 32: Indicates "Mild to Moderate" alcoholic hepatitis. These patients generally have a low risk of short-term mortality (less than 10% at 30 days) and typically do not require steroid intervention.
  • DF Score ≥ 32: Indicates "Severe" alcoholic hepatitis. This threshold is associated with a 30-day mortality rate as high as 35-50% without treatment. Steroid therapy is strongly indicated if no contraindications (like active infection) exist.

Standard Dosage Recommendation

For patients with a Carithers Index/Maddrey score of 32 or higher, the standard treatment protocol established by clinical trials is:

  • Medication: Prednisolone (preferred over Prednisone as it does not require hepatic metabolism).
  • Dosage: 40 mg orally once daily.
  • Duration: 28 days, followed by a taper (e.g., tapering over 2-4 weeks) or immediate cessation depending on the Lille Model reassessment at day 7.

Example Calculation

Consider a patient with a PT of 24 seconds, a control PT of 12 seconds, and a Bilirubin of 14 mg/dL:

Calculation: 4.6 × (24 – 12) + 14 = 4.6 × 12 + 14 = 55.2 + 14 = 69.2

With a score of 69.2, this patient falls into the severe category (DF > 32) and should be evaluated for 40mg daily prednisolone therapy.

function calculateCarithers() { var ptPatient = parseFloat(document.getElementById('ptPatient').value); var ptControl = parseFloat(document.getElementById('ptControl').value); var bilirubin = parseFloat(document.getElementById('bilirubin').value); var resultsArea = document.getElementById('resultsArea'); var dfScoreDisplay = document.getElementById('dfScoreDisplay'); var severityStatus = document.getElementById('severityStatus'); var dosageRec = document.getElementById('dosageRecommendation'); if (isNaN(ptPatient) || isNaN(ptControl) || isNaN(bilirubin)) { alert("Please enter valid numerical values for all fields."); return; } // Formula: 4.6 * (Patient PT – Control PT) + Total Bilirubin var ptDifference = ptPatient – ptControl; var dfScore = (4.6 * ptDifference) + bilirubin; var roundedScore = dfScore.toFixed(2); resultsArea.style.display = 'block'; dfScoreDisplay.innerHTML = "DF Score: " + roundedScore; if (dfScore >= 32) { resultsArea.style.backgroundColor = '#fff3f3'; resultsArea.style.border = '1px solid #f5c6cb'; severityStatus.innerHTML = "STATUS: SEVERE ALCOHOLIC HEPATITIS"; severityStatus.style.color = '#721c24'; dosageRec.innerHTML = "Clinical Recommendation:A score ≥ 32 indicates high short-term mortality risk. Corticosteroid therapy is indicated.Typical Dosage: Prednisolone 40 mg daily for 28 days. Monitor response using the Lille Model at day 7."; } else { resultsArea.style.backgroundColor = '#d4edda'; resultsArea.style.border = '1px solid #c3e6cb'; severityStatus.innerHTML = "STATUS: MILD TO MODERATE"; severityStatus.style.color = '#155724'; dosageRec.innerHTML = "Clinical Recommendation:A score < 32 indicates lower risk. Corticosteroids are generally not indicated for survival benefit in this range. Supportive care and alcohol abstinence are primary management goals."; } }

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