How to Calculate Bilirubin Rate of Rise

Bilirubin Rate of Rise Calculator

Calculate the hourly increase in Total Serum Bilirubin (TSB).

How to Calculate Bilirubin Rate of Rise

In neonatal medicine, monitoring the Bilirubin Rate of Rise (ROR) is a critical step in managing newborn jaundice (hyperbilirubinemia). The rate at which Total Serum Bilirubin (TSB) increases helps clinicians identify infants at risk for severe jaundice and potential neurotoxicity. A rapid rise often indicates a pathological process, such as hemolysis (breakdown of red blood cells), rather than simple physiological jaundice.

The Calculation Formula

The rate of rise is calculated by determining the difference between two bilirubin measurements and dividing it by the time elapsed between those measurements.

Rate of Rise = (Second TSB – First TSB) / Time Elapsed (Hours)

Where:

• Second TSB: The most recent bilirubin level in mg/dL.
• First TSB: The previous bilirubin level in mg/dL.
• Time Elapsed: The duration in hours between the two blood draws.

Interpretation of Results

The rate of rise provides insight into the underlying cause of the jaundice. While specific protocols vary by institution, general guidelines suggest:

• < 0.2 mg/dL per hour: This is often observed in physiological jaundice. However, the absolute level must still be plotted on the Bhutani nomogram or specific treatment graphs (like AAP guidelines) to determine if phototherapy is needed.
• > 0.2 mg/dL per hour: A rise greater than 0.2 mg/dL/hr suggests increased bilirubin production and may indicate hemolysis. Closer monitoring is typically required.
• > 0.5 mg/dL per hour: This is considered a rapid rate of rise. It is highly suggestive of severe hemolysis (e.g., ABO incompatibility, Rh disease, G6PD deficiency) and often requires immediate intervention, such as intensive phototherapy or consideration for exchange transfusion depending on the total TSB level.

Clinical Example

Consider a newborn who had a TSB of 5.0 mg/dL at 24 hours of life. A repeat test at 30 hours of life shows a TSB of 6.8 mg/dL.

• Change in TSB: 6.8 – 5.0 = 1.8 mg/dL
• Time Elapsed: 30 – 24 = 6 hours
• Calculation: 1.8 / 6 = 0.3 mg/dL per hour

In this example, the rate of 0.3 mg/dL/hr exceeds the 0.2 threshold, warranting further investigation for hemolytic causes.

Why Monitoring the Rate Matters

The absolute bilirubin number is important, but the velocity of the increase predicts the trajectory. A baby with a low bilirubin level that is rising very fast is more concerning than a baby with a slightly higher level that is stable or falling. Early identification of a high rate of rise allows for early initiation of phototherapy, preventing bilirubin levels from reaching dangerous thresholds that could cause kernicterus.

function calculateBiliRate() { var initialVal = document.getElementById("initialTSB").value; var finalVal = document.getElementById("finalTSB").value; var timeVal = document.getElementById("timeElapsed").value; var resultBox = document.getElementById("biliResult"); // Input Validation if (initialVal === "" || finalVal === "" || timeVal === "") { resultBox.style.display = "block"; resultBox.innerHTML = "Please fill in all fields to calculate the rate."; return; } var tsb1 = parseFloat(initialVal); var tsb2 = parseFloat(finalVal); var hours = parseFloat(timeVal); if (isNaN(tsb1) || isNaN(tsb2) || isNaN(hours)) { resultBox.style.display = "block"; resultBox.innerHTML = "Please enter valid numbers."; return; } if (hours <= 0) { resultBox.style.display = "block"; resultBox.innerHTML = "Time elapsed must be greater than zero."; return; } // Calculation var difference = tsb2 – tsb1; var rateOfRise = difference / hours; var rateFormatted = rateOfRise.toFixed(2); // Interpretation Logic var interpretation = ""; var alertClass = ""; if (rateOfRise = 0.5) { interpretation = "Warning: Rapid Rise. Rate > 0.5 mg/dL/hr is highly suggestive of hemolysis. Urgent evaluation required."; alertClass = "alert-high"; } else if (rateOfRise > 0.2) { interpretation = "Caution: Significant Rise. Rate > 0.2 mg/dL/hr may suggest hemolysis or increased production."; alertClass = "alert-high"; // Using high color for caution } else { interpretation = "Rate of rise is < 0.2 mg/dL/hr. This is generally consistent with physiological trends, but always interpret in context of the absolute TSB level and infant age."; alertClass = "alert-normal"; } // Construct Result HTML var resultHTML = ''; resultHTML += ''; resultHTML += '

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'; resultHTML += ''; resultHTML += ''; resultHTML += " + interpretation + "; resultBox.style.display = "block"; resultBox.innerHTML = resultHTML; }