Calculate the I/T ratio (immature to total neutrophils) for newborn sepsis screening from CBC differential percentages or from immature and total counts.
Related Calculators
- Neutrophil-Lymphocyte Ratio Calculator
- Platelet-Lymphocyte Ratio Calculator
- WBC Calculator
- Absolute Lymphocyte Count Calculator
- BUN Creatinine Ratio Calculator
- International Normalized Ratio Calculator
- All Math and Numbers Calculators
IT Ratio Formula
Formula reference: Texas Children’s Hospital – Recognition of Neonatal Sepsis Workshop Slides (2024)
Clinical interpretation: Canadian Paediatric Society; Hornik et al., 2012. CBC indices alone cannot reliably rule out early-onset sepsis.
Where ITR is the I/T ratio (fraction 0 to 1, or percent), IN is the total immature neutrophil count, and TN is the total neutrophil count including both mature segmented forms and all immature precursors.
What counts as immature: this tool includes bands, metamyelocytes, myelocytes and promyelocytes. Total neutrophils also include segmented forms. Check the laboratory definition; automated IG% may omit bands and is not automatically equivalent to a manual I/T ratio.
I/T Ratio Reference Ranges
Reference intervals depend on the population, sample timing and laboratory method. The calculator assumes no age-based diagnostic cutoff; an optional clinician-supplied reference is compared arithmetically.
| Reference context | Calculator behavior |
|---|---|
| Age and clinical protocol | No universal reference range assumed |
| Optional reference | Comparison only; no diagnosis |
| Below reference | Does not exclude infection |
An elevated ratio may be associated with infection, but a low ratio does not reliably exclude early-onset neonatal sepsis. The calculator does not return a sepsis diagnosis or a normal-range verdict.
Diagnostic Performance
| Measure | Interpretive limit |
|---|---|
| Sensitivity | A low ratio can occur with infection |
| Specificity | Elevation can have non-infectious causes |
| Predictive values | Depend on prevalence and study population |
Predictive values depend on the study population and prevalence. Do not apply a universal sensitivity, specificity or negative predictive value to an individual result.
Non-Infectious Causes of Elevated I/T Ratio
Non-infectious physiologic stress can also affect a neonatal differential. Clinical context and sample timing matter; an isolated ratio does not identify the cause.
I/T Ratio vs. Other Neonatal Sepsis Markers
| Marker | Role in this calculator |
|---|---|
| I/T | Immature divided by all included neutrophils |
| Segs + bands | Simplified mode; other immature forms assumed zero |
| WBC | Optional absolute-count arithmetic |
| CRP / PCT / cultures | Not interpreted by this calculator |
Neither this ratio nor a single inflammatory-marker result should be used alone to determine whether neonatal sepsis is present or excluded.
I/T2 Ratio
I/T² is a separate proposed index that combines immature and total neutrophil counts. This calculator reports I/T, not I/T², and does not infer diagnostic accuracy or treatment from either.
CBC Timing and Serial Monitoring
CBC interpretation depends on postnatal age and the infant’s clinical condition. Decisions about whether and when to repeat tests belong to the treating team and the applicable neonatal protocol.
