Pediatric CBC Reference Values: Age-Specific Interpretation Chart
Use age-specific, analyzer-specific, and reagent-specific reference ranges when interpreting pediatric CBC results, as applying adult reference ranges to children can misclassify up to 30% of normal children as abnormal. 1
Critical Principle: Developmental Hemostasis
Children's hematologic values change dramatically with age, and laboratories must use standardized age groupings (neonates, 1 month-1 year, 1-5 years, 6-10 years, 11-16 years) that reflect statistically different physiological states. 1 Using inappropriate reference ranges leads to misdiagnosis, unnecessary testing, surgical cancellations, and long-term psychological impact on families. 1
Age-Specific Hemoglobin Reference Ranges
Normal hemoglobin values vary significantly by age and sex in pediatric patients: 1
Key Hemoglobin Thresholds by Age:
- Neonates and infants <3 months: Higher thresholds apply; specific values depend on gestational age and postnatal age in hours 2
- Children >3 months: Restrictive threshold of <70 g/L is appropriate for most stable, non-bleeding children 1
- Critically ill children: Maintain hemoglobin >70 g/L even in conditions with limited oxygen delivery (septic shock, traumatic brain injury, post-cardiac surgery) 1
- Neonates and congenital heart disease: Higher thresholds often applied, though moderately restrictive approaches can reduce transfusion volumes without adverse outcomes 1
The hemoglobin concentration increases with age and is generally higher in males than females, particularly after puberty. 3
White Blood Cell Parameters
White blood cell counts remain relatively stable from 3 months to 18 years without obvious upward or downward trends. 3 However, interpretation requires careful attention to:
Neutrophil Assessment:
- Severe neutropenia (ANC <200/mm³) requires urgent hematology consultation and consideration of growth factor support 4
- Mean absolute neutrophil counts (ANCs) are lower in infected newborns, with discrimination improving significantly with age in the first hours of life 2
- Very low values are most informative: ANC <1000 at ≥4 hours of age has a likelihood ratio of 115 for infection 2
Age-Specific Interpretation in Neonates:
White blood cell counts and ANCs show poor discrimination at <1 hour of age (area under ROC curve 0.52) but excellent discrimination at ≥4 hours (area under ROC curve 0.87). 2 Optimal interpretation requires using interval likelihood ratios specific to the newborn's age in hours. 2
Red Blood Cell Parameters
Most red blood cell-related parameters increase with age and are generally higher in males than females. 3
Key Red Cell Indices:
- MCV (Mean Corpuscular Volume): May indicate macrocytosis as a manifestation of myelodysplastic syndrome in at-risk patients 4
- Red cell distribution width: Should be evaluated as part of comprehensive CBC assessment 5
- Hematocrit levels follow similar age and sex patterns as hemoglobin 5
Platelet Parameters
Platelet levels decrease within the first year of life and tend to stabilize thereafter. 3
Thrombocytopenia Management:
- Grade 2-3 immune thrombocytopenia: Consider prednisone 1 mg/kg/day (0.5-2 mg/kg/day) orally for 2-4 weeks with 4-6 week taper 4
- Grade 4 cases: Require hematology consultation and prednisone 1-2 mg/kg/day (oral or IV depending on symptoms) 4
- In obstetric hemorrhage context, platelet transfusion indicated when count <75 × 10⁹/L 1
Pediatric Blood Component Dosing
Blood products in children should be prescribed by volume rather than number of units: 1
- RBC transfusion: 10 ml/kg should increase hemoglobin by approximately 20 g/L 1
- Cryoprecipitate: 5-10 ml/kg 1
- Platelets: 10-20 ml/kg 1
- FFP: 10-15 ml/kg 1
Critical Pitfalls to Avoid
Never use adult reference ranges for pediatric samples, as this leads to systematic misclassification. 1 Approximately 30% of healthy 1-5 year olds would be classified as abnormal using adult ranges. 1
Reagent-specific differences matter: The APTT reference range decreases with age using PTT-A reagent but increases with age using Cephascreen reagent from the same manufacturer. 1 Only use published ranges established with identical analyzer and reagent systems. 1
Timing matters in neonates: CBC interpretation in the first 72 hours requires age-in-hours-specific interpretation, particularly for WBC and ANC values. 2 Tests performed at <1 hour have poor predictive value compared to those at ≥4 hours. 2
When to Refer to Hematology
Immediate hematology consultation is indicated for: 4
- Severe cytopenias (Grade 3-4) affecting any cell line
- Multiple cell line abnormalities suggesting bone marrow failure
- Presence of blasts or significant dysplastic changes on peripheral smear
- Persistent unexplained cytopenias despite initial evaluation
- Suspected hematologic malignancy based on clinical or laboratory findings
Follow-Up Monitoring
For high-risk patients (MDS/AML risk): 4
- CBC every 3-4 months for highest risk conditions
- CBC every 6-12 months for moderate risk conditions if counts remain stable
For isolated mild abnormalities with otherwise normal CBC: Repeat CBC in 3 months to establish stability or identify trends. 4
Baseline Screening Recommendation
Every child should have baseline hematology evaluation with hemoglobin and hematocrit starting at age 12 months, or younger if clinically indicated. 6 This establishes individual baseline values for future comparison.