Should a child with a positive Immunoglobulin E (IgE) to peanut be referred to an allergist?

Referral to Allergist for Children with Positive IgE to Peanut

Yes, a child with a positive IgE to peanut (≥0.35 kUA/L) should be referred to an allergist for further evaluation and management to reduce morbidity and mortality risks associated with potential peanut allergy. 1

Decision Algorithm Based on Peanut-Specific IgE Results

For Positive Peanut-Specific IgE (≥0.35 kUA/L):

• Refer to allergist for further consultation and possible skin prick testing
• Do not introduce peanut into the diet until specialist evaluation is complete
• The specialist will determine if peanut can be safely introduced and the appropriate method

For Negative Peanut-Specific IgE (<0.35 kUA/L):

• Peanut can be introduced at home without specialist referral
• Consider supervised feeding in healthcare provider's office if there are concerns

Rationale for Allergist Referral

The National Institute of Allergy and Infectious Diseases (NIAID) expert panel emphasizes that peanut-specific IgE ≥0.35 kUA/L lacks adequate positive predictive value for diagnosing peanut allergy 1. Therefore, specialist evaluation is necessary to:

1. Determine true clinical reactivity through skin prick testing and possibly oral food challenges
2. Assess risk of severe allergic reactions
3. Provide appropriate guidance on peanut introduction or avoidance
4. Develop an emergency action plan if needed

Specialist Evaluation Process

The allergist will typically:

• Perform skin prick testing with peanut extract
• Categorize risk based on wheal diameter:
  • ≤2 mm: Low risk - peanut can be introduced at home
  • 3-7 mm: Moderate risk - supervised feeding or graded oral food challenge recommended
  • ≥8 mm: High risk - likely peanut allergic, typically requiring strict avoidance 1

Clinical Implications and Considerations

Risk Stratification

Research shows that specific IgE levels correlate with clinical reactivity:

• A specific IgE >5 kU/L significantly increases the likelihood of a positive food challenge (OR 3.35; 95% CI 1.23-9.11) 2
• Skin prick test ≥8 mm has a 95% predictive value for clinical peanut allergy 3

Component Testing Considerations

• Beyond standard peanut-specific IgE, component testing (especially for Ara h 2 and Ara h 6) may provide additional diagnostic information
• Ara h 2 sensitization is strongly associated with clinical peanut allergy, though 26% of sensitized but tolerant patients may also show IgE binding to Ara h 2 4
• In rare cases, patients may have significant Ara h 6 sensitization with minimal Ara h 2 sensitization but still experience severe reactions 5

Special Considerations for High-Risk Infants

For infants with severe eczema and/or egg allergy:

• Early introduction of peanut (4-6 months) is recommended to prevent peanut allergy
• Evaluation by an allergist before introduction is strongly advised 1
• The allergist can determine the appropriate method for peanut introduction based on testing results

Common Pitfalls to Avoid

1. Misinterpreting positive IgE results: A positive peanut-specific IgE alone does not confirm clinical allergy but indicates sensitization

2. Delaying specialist referral: Timely evaluation is important, especially for high-risk infants who may benefit from early peanut introduction

3. Relying solely on IgE levels: Neither specific IgE to peanut nor to Ara h 2 alone can perfectly distinguish between clinical allergy and sensitization without clinical reactivity 4

4. Unnecessary food avoidance: Avoiding peanut based solely on positive IgE without specialist evaluation may lead to unnecessary dietary restrictions and potentially increase allergy risk

5. Overlooking emergency preparedness: While awaiting specialist evaluation, ensure appropriate emergency medications are prescribed if there's concern for potential severe reactions 1