1. What is the I/T Ratio?

The I/T (Immature to Total neutrophil) ratio is a measure used in newborn medicine to assess the likelihood of bacterial infection. It compares the number of immature neutrophils to the total neutrophil count in a blood sample.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( Immature\_neutrophils \) — Count of immature neutrophils (bands and earlier forms)
• \( Total\_neutrophils \) — Count of all neutrophils (mature + immature)

Explanation: The ratio helps identify a "left shift" in neutrophil maturation, which can indicate infection or inflammation.

3. Importance of I/T Ratio in Newborns

Details: In neonates, an I/T ratio >0.2 is often considered abnormal and may suggest early-onset sepsis, particularly when combined with other clinical signs.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is a normal I/T ratio in newborns?
A: Typically <0.2 in healthy term infants. Values >0.2 may indicate infection but should be interpreted in clinical context.

Q2: How accurate is the I/T ratio for sepsis?
A: Sensitivity is moderate (~60-80%), so normal values don't rule out infection. Specificity is better (~85-90%).

Q3: Does gestational age affect the I/T ratio?
A: Yes, premature infants may have slightly higher normal ranges. Always consult gestational age-specific norms.

Q4: When should I/T ratio be measured?
A: When evaluating for early-onset sepsis (first 72 hours of life), especially with risk factors like maternal fever or chorioamnionitis.

Q5: What other tests complement the I/T ratio?
A: CRP, procalcitonin, complete blood count, blood cultures, and clinical assessment provide a more complete picture.