function calculateRateOfRise() {
// 1. Get Input Values
var initialLevel = parseFloat(document.getElementById('initialLevel').value);
var initialTimeInput = document.getElementById('initialTime').value;
var currentLevel = parseFloat(document.getElementById('currentLevel').value);
var currentTimeInput = document.getElementById('currentTime').value;
// 2. Validation
if (isNaN(initialLevel) || isNaN(currentLevel) || !initialTimeInput || !currentTimeInput) {
alert("Please enter valid bilirubin levels and times.");
return;
}
var date1 = new Date(initialTimeInput);
var date2 = new Date(currentTimeInput);
// Check if dates are valid
if (isNaN(date1.getTime()) || isNaN(date2.getTime())) {
alert("Please enter valid dates.");
return;
}
// Calculate time difference in milliseconds
var diffMs = date2 – date1;
if (diffMs 0.2) {
note = "Note: A rate of rise greater than 0.2 mg/dL/hr usually suggests hemolysis.";
document.getElementById('clinical-note').style.color = "#d35400";
} else {
note = "Note: Rate is below the typical threshold for suspected active hemolysis (0.2 mg/dL/hr).";
document.getElementById('clinical-note').style.color = "#27ae60";
}
document.getElementById('clinical-note').innerHTML = note;
}
How to Calculate Rate of Rise of Bilirubin
Monitoring the rate of rise in bilirubin levels is a critical component in the assessment of neonatal jaundice (hyperbilirubinemia). Rapid increases in Total Serum Bilirubin (TSB) often indicate pathological processes, such as hemolysis (the breakdown of red blood cells), rather than simple physiological jaundice.
Clinical Relevance: Identifying a rapid rate of rise helps clinicians decide when to initiate phototherapy or perform further diagnostic workups to prevent complications like kernicterus.
The Rate of Rise Formula
To calculate the rate of rise, you need two separate bilirubin measurements taken at different times. The formula determines the velocity at which bilirubin is accumulating in the blood.
Rate of Rise = (Current Bilirubin – Initial Bilirubin) / Time Interval in Hours
Variables Explained:
Initial Bilirubin: The first TSB measurement (usually in mg/dL).
Current Bilirubin: The follow-up TSB measurement.
Time Interval: The elapsed time between the two blood draws, calculated in hours.
Step-by-Step Calculation Example
Let's look at a practical example of how to calculate the rate of rise manually:
First Measurement: A newborn has a TSB of 5.0 mg/dL at 8:00 AM.
Second Measurement: A follow-up test shows a TSB of 6.2 mg/dL at 2:00 PM the same day.
Calculate Change in Bilirubin: 6.2 – 5.0 = 1.2 mg/dL.
Calculate Time Elapsed: From 8:00 AM to 2:00 PM is 6 hours.
Divide: 1.2 mg/dL / 6 hours = 0.2 mg/dL per hour.
Interpreting the Results
While guidelines vary by institution and country (e.g., AAP vs. NICE guidelines), the rate of rise provides specific clues regarding the etiology of the jaundice.
Thresholds of Concern
> 0.2 mg/dL per hour: This is a common threshold used to suggest hemolysis (immune or non-immune). It typically necessitates a Coombs test, reticulocyte count, and blood type check.
> 5.0 mg/dL per day: If monitoring over a 24-hour period, an increase greater than 5 mg/dL is generally considered pathological.
Why is Rate of Rise Important?
Absolute bilirubin levels are plotted on nomograms (such as the Bhutani nomogram) to determine risk zones. However, the rate provides a dynamic view. A baby might be in a "low risk" zone initially, but a high rate of rise could propel them into a "high risk" zone quickly. Calculating the velocity allows for:
Early initiation of phototherapy.
Early preparation for exchange transfusion if the rate is uncontrollable.
Identification of ABO incompatibility or G6PD deficiency.
Factors Affecting Bilirubin Levels
When calculating the rate of rise, consider factors that influence bilirubin metabolism:
Gestational Age: Preterm infants are more susceptible to neurotoxicity at lower levels.
Feeding: Breastfeeding jaundice or breast milk jaundice can influence levels, though usually with a slower rise than hemolysis.
Bruising/Cephalohematoma: Extravasated blood breaking down can increase the bilirubin load.
Disclaimer: This calculator is for educational and informational purposes only. It is not a medical device. Always consult a pediatrician or neonatologist for medical decisions regarding neonatal care.