1. What is the I/T Ratio?

The I/T (Immature to Total) neutrophil ratio is a calculation used in pediatrics to assess the severity of bacterial infections, particularly in neonates. It compares the number of immature neutrophils (band forms and earlier precursors) to the total neutrophil count.

2. How Does the Calculator Work?

The calculator uses the I/T ratio formula:

Where:

• \( Immature\_neutrophils \) — Count of band forms and earlier neutrophil precursors
• \( Total\_neutrophils \) — Sum of mature and immature neutrophils

Explanation: The ratio helps differentiate between bacterial and viral infections, with higher ratios suggesting bacterial infection.

3. Importance of I/T Ratio in Pediatrics

Details: The I/T ratio is particularly valuable in neonatal sepsis evaluation. A ratio >0.2 in term infants or >0.25 in preterm infants suggests high likelihood of bacterial infection.

4. Using the Calculator

Tips: Enter the absolute counts of immature neutrophils and total neutrophils from a complete blood count (CBC) with differential. Both values must be positive numbers with total neutrophils greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal I/T ratio in newborns?
A: In healthy term newborns, the I/T ratio is typically <0.2. Values above this threshold may indicate infection.

Q2: How sensitive is the I/T ratio for neonatal sepsis?
A: Sensitivity ranges from 60-90% depending on the population and cutoff used, with specificity around 70-80%.

Q3: Does the I/T ratio change with age?
A: Yes, the ratio is highest at birth and decreases over the first few days of life. Different cutoffs may apply for preterm infants.

Q4: What other tests should accompany the I/T ratio?
A: The ratio is most useful when combined with clinical assessment, CRP, procalcitonin, and blood cultures.

Q5: Can medications affect the I/T ratio?
A: Yes, maternal antibiotics, steroids, and stress can all influence neutrophil counts and maturation.