Normal Values of Total Serum IgE for Adults
The upper limit of normal for total serum IgE in adults is generally accepted as 100-150 IU/mL (or kU/L), though this varies by age, with geometric mean values around 14-32 IU/mL in healthy non-atopic adults. 1, 2
Age-Specific Reference Ranges
The normal range for total serum IgE varies significantly by age group in adults:
- Young adults (18-30 years): Upper limit approximately 100 IU/mL 2
- Middle-aged adults (31-64 years): Upper limit approximately 100-120 IU/mL 2
- Older adults (≥65 years): Upper limit approximately 100-120 IU/mL 2
The geometric mean for healthy non-atopic adults ranges from 14-32 IU/mL, with the 95th percentile reaching 100-150 IU/mL. 1, 2, 3
Critical Interpretation Considerations
Defining a single "normal" cutoff for IgE is of limited clinical utility because there is enormous overlap between healthy individuals and those with allergic disease. 1
Key Limitations:
- Wide distribution: Individual IgE values in healthy adults can range from <1 IU/mL to >400 IU/mL, even in those without allergic disease 1, 3
- Poor discrimination: No single IgE level reliably distinguishes between allergic and non-allergic individuals 1
- Population variation: Reference ranges differ by geographic location and population studied 2
Clinical Context for Elevated Values
When IgE levels exceed normal ranges, consider these disease-specific patterns:
Moderately Elevated (150-500 IU/mL):
- Allergic rhinitis (geometric mean 171 IU/mL) 2
- Eczema alone (geometric mean 273 IU/mL) 2
- Various eczematous conditions 4
Markedly Elevated (>500 IU/mL):
- ABPA diagnosis: IgE >500 IU/mL is a diagnostic criterion, though >1000 IU/mL has 97.5% sensitivity in asthmatic patients 5
- Asthma (geometric mean 305 IU/mL) 2
- Combined asthma and eczema (geometric mean 985 IU/mL) 2
Very High Levels (≥1000 IU/mL):
- Associated with increased risk of cardiovascular disease in adults aged 31-64 years 6
- Increased risk of eosinophilic disorders across all age groups 6
- Possible association with inborn errors of immunity 6
Important Clinical Caveats
Total IgE measurement has limited diagnostic value when used in isolation because:
- Many allergic patients have normal IgE levels 3
- Many non-allergic conditions cause elevated IgE (parasitic infections, certain malignancies, autoimmune conditions) 4, 6
- IgE levels do not correlate reliably with disease activity in all conditions 7
Logarithmic conversion is necessary for statistical analysis because IgE values follow a log-normal rather than normal distribution. 3
For diagnostic purposes, specific IgE testing or skin prick testing to identify particular allergens is more clinically useful than total IgE alone, with negative predictive values >95%. 7