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I/T Ratio Formula:
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The I/T (Immature to Total Neutrophils) ratio is a calculation used in newborn medicine to assess the risk of early-onset sepsis. It compares the number of immature neutrophils to the total neutrophil count in a blood sample.
The calculator uses the I/T ratio formula:
Where:
Explanation: The ratio provides a quantitative measure of the left shift in neutrophil production, which is often increased in bacterial infections.
Details: The I/T ratio is a valuable screening tool for neonatal sepsis. A ratio greater than 0.2-0.3 is often considered abnormal and may indicate infection, particularly in the first 72 hours of life.
Tips: Enter the immature neutrophil count and total neutrophil count from a complete blood count (CBC) with manual differential. Both values must be valid (counts ≥ 0, total neutrophils > 0).
Q1: What is a normal I/T ratio in newborns?
A: In healthy term newborns, the I/T ratio is typically less than 0.16 during the first 60 hours of life. Values above 0.2-0.3 are considered abnormal and may suggest infection.
Q2: How is the I/T ratio used clinically?
A: The I/T ratio is used as part of sepsis evaluation in newborns, along with other clinical findings and laboratory tests. It helps guide decisions about antibiotic therapy.
Q3: Does the I/T ratio change with gestational age?
A: Yes, preterm infants may have slightly higher normal I/T ratios compared to term infants. Reference ranges should be adjusted based on gestational age.
Q4: What are the limitations of the I/T ratio?
A: The I/T ratio has limited specificity and can be elevated in non-infectious conditions such as maternal fever, perinatal asphyxia, or hemolytic disease.
Q5: How soon after birth should the I/T ratio be measured?
A: The I/T ratio is most useful in the first 24-72 hours of life for evaluating early-onset sepsis. Serial measurements may be helpful in monitoring response to treatment.