From the Guidelines
IgE skin testing is the most reliable test for detecting the presence of specific immunoglobulin E (IgE) antibodies. This test directly measures the presence of IgE antibodies by introducing small amounts of suspected allergens into the skin and observing for a local allergic reaction. When an allergen is introduced to the skin of a sensitized person, it binds to IgE antibodies on mast cells, triggering the release of histamine and other inflammatory mediators that cause a visible wheal and flare reaction within minutes. The size of this reaction correlates with the amount of specific IgE present.
Key Points to Consider
- While other tests like nasal smears for eosinophils may indicate allergic inflammation, and blood tests like CBC might show elevated eosinophil counts, these are indirect markers.
- Complete metabolic panel (CMP) evaluates organ function and has no role in IgE detection.
- Western blot analysis, though useful for detecting proteins, is not the standard method for clinical IgE testing due to its complexity and cost compared to the more efficient and sensitive skin testing method.
Evidence Supporting Skin Testing
Studies have shown that skin testing is generally more sensitive than in vitro IgE tests in detecting allergen-specific IgE 1. The European position paper on rhinosinusitis and nasal polyps 2020 also supports the use of skin prick testing or serum specific IgE for measuring sensitization in regular clinical practice 1.
Advantages of Skin Testing
- Allows for direct observation of the body’s reaction to a specific antigen
- Not affected by patient’s medications
- Can be used for patients with skin conditions such as dermatographism or severe eczema
- Less expensive than blood testing
- Can be used for patients on β-blockers or with comorbid medical conditions that preclude skin testing
Limitations and Alternatives
- Skin testing may be affected by patient medications
- May have possible systemic allergic reaction (anaphylaxis)
- In vitro tests, such as serum specific IgE, can be used as an alternative to skin tests in certain situations, such as in patients with dermatographism or atopic dermatitis 1.
From the Research
Most Reliable Test for Detecting Specific Immunoglobulin E (IgE) Antibodies
- The most reliable test for detecting the presence of specific IgE antibodies is IgE skin testing, as it remains unexcelled as a sensitive and cost-efficient test for specific IgE 2.
- Skin prick testing is considered the first line approach in most instances for detecting IgE sensitization 3.
- In vitro tests, such as enzyme-linked immunosorbent assay (ELISA), can be used as substitutes for skin tests in certain circumstances, but they may have limitations in terms of sensitivity and specificity 2, 4, 5.
- Other options, such as nasal smear for eosinophils, complete blood count (CBC), and Western blot analysis, are not considered the most reliable tests for detecting specific IgE antibodies.
- It is essential to note that positive tests for allergen-specific IgE do not diagnose allergy, but rather indicate the presence of IgE molecules with a particular immunologic specificity 2.