Laboratory Values Assessment for 1-Year-Old Male
These laboratory values are entirely normal for a 1-year-old child and require no intervention or further workup in the absence of clinical symptoms.
Normal Reference Ranges for Age
The provided values fall within expected parameters for this age group:
- WBC 4.9 × 10⁹/L: Normal (reference range approximately 6.0-17.5 × 10⁹/L for infants, though values as low as 3.69-9.16 × 10⁹/L are within normal limits for some populations) 1, 2
- RBC 3.87 × 10¹²/L: Normal (reference range 3.68-5.13 × 10¹²/L) 2
- MCV 89.9 fL: Normal (reference range 82.6-99.1 fL) 2
- Absolute Neutrophil Count (ANC) 5110/mm³: Normal and reassuring 1
- Absolute Lymphocyte Count (ALC) 3567/mm³: Normal with physiologic lymphocyte predominance expected at this age 1
Clinical Context Determines Significance
If the child is asymptomatic, these values require no action. The WBC count, while at the lower end of some reference ranges, is not concerning when the absolute neutrophil count is adequate (>1500/mm³) 3.
If the child has fever or respiratory symptoms, the WBC of 4.9 × 10⁹/L would be consistent with viral illness, particularly influenza, where low WBC (<5.0) occurs in 24% of cases and lymphopenia occurs in 40% of cases 4. However, this child's lymphocyte count is normal, not low 1.
Key Clinical Decision Points
When These Values Would Be Concerning:
- Fever >39°C with WBC >15,000/mm³: Would indicate increased risk for serious bacterial infection requiring blood culture and possible empiric antibiotics 1, 5
- WBC <5,000/mm³ with severe lymphopenia (<1,000/mm³): Would suggest severe viral infection or, in the context of H5N1 influenza, carries high mortality risk 4
- ANC <1,000/mm³: Would significantly increase infection risk and require urgent evaluation 3
This Child's Values Do NOT Meet Concerning Criteria:
- WBC is not severely low (<4.0 × 10⁹/L) 4
- ANC is robust at 5110/mm³, well above the concerning threshold of <1,000/mm³ 3
- Lymphocyte count is normal, not lymphopenic 1
- No indication of leukocytosis (>15,000/mm³) that would suggest bacterial infection 1, 5
Recommended Action
No further laboratory evaluation or clinical intervention is needed if the child is asymptomatic 3.
If clinical symptoms develop (fever, signs of infection, unexplained bleeding/bruising), immediate evaluation would be warranted with repeat CBC with differential 3, 1.
Common Pitfalls to Avoid
- Do not assume infection is ruled out by normal WBC, as some serious infections can present with normal counts 3
- Do not ignore the absolute neutrophil count, which is more clinically significant than total WBC and is reassuringly normal here 3
- Do not order unnecessary repeat testing in an asymptomatic child with values this close to normal ranges 3
- Do not overlook clinical context: Laboratory values must always be interpreted alongside clinical presentation, not in isolation 1, 5