Normal White Blood Cell Count for a 10-Month-Old
The normal total white blood cell (WBC) count for a 10-month-old infant ranges from approximately 6,000-17,500/mm³, with lymphocyte predominance being the expected physiologic pattern at this age 1.
Age-Specific Physiologic Patterns
At 10 months of age, several key hematologic characteristics are normal:
- Total WBC count: The normal range is approximately 6,000-17,500/mm³, which is higher than adult values 1
- Lymphocyte predominance: Lymphocytes are the predominant white blood cell type at this age, which is physiologically normal 1, 2
- CD4 cell count: For infants from birth through 12 months, the normal CD4 count is ≥1,500 cells/mm³, which is substantially higher than adult ranges 3
Critical Thresholds for Clinical Interpretation
Understanding when WBC counts indicate potential pathology is essential:
Elevated WBC Counts
- WBC >15,000/mm³: Suggests possible bacterial infection, particularly when combined with fever >39°C 1, 4
- WBC ≥35,000/mm³: Considered extreme leukocytosis in pediatric emergency settings, with 26% of such cases having serious disease and 10% having bacteremia 5
Low WBC Counts
- WBC <5,000/mm³: May indicate viral illness (occurs in 8-27% of children with influenza A) 3, 6
- WBC <1,500/mm³ with lymphopenia: Indicates severe infection requiring immediate evaluation and carries high mortality risk 7, 6
Clinical Context Matters
The interpretation of WBC counts in a 10-month-old must account for clinical presentation:
- Febrile infant with WBC >15,000/mm³: Consider blood culture, urinalysis, and evaluation for focal bacterial infection 1
- Asymptomatic infant: Values within the 6,000-17,500/mm³ range are normal and require no intervention 1
- Ill-appearing infant with low WBC: Requires full diagnostic evaluation including blood culture, complete blood count with differential, and consideration of lumbar puncture if stable 7
Important Caveats
- Lymphocyte-neutrophil crossover: At approximately 5 years of age, neutrophils become the predominant cell type, but at 10 months, lymphocyte predominance is expected 2
- Individual variation: While the reference range is 6,000-17,500/mm³, the 2.5th and 97.5th percentiles define the boundaries, meaning some healthy infants may fall slightly outside these values 2
- Avoid over-reliance on WBC alone: In febrile infants <90 days old, WBC ≥15,000/mm³ has only 13.6% sensitivity and 85% specificity for serious bacterial infection, making it unreliable as a sole diagnostic tool 8