IgE MicroAssay™

FACT SHEET

The Touch Tear IgE MicroAssay Kit™ is an in vitro diagnostic device that is used for the quantitative determination of Immunoglobulin E (IgE) concentration in tears. It is also used as an aid in the diagnosis of ocular Type-1 allergic conjunctivitis or the allergic component of ocular inflammatory responses. A complete description is contained in the Package Insert.

Brief Summary

Elevated levels of IgE indicate an IgE-mediated hypersensitivity, responsible for Type-1 (anaphylactic) allergic reactions. The reaction includes inflammation, constriction of smooth muscles, dilation of blood vessels, and irritation of nerve endings characteristic of allergic reactions. Clinical symptoms include inflammation, itching (skin), congestion (bronchial), or hyperemia (ocular). In ocular allergies, tear concentrations of IgE may be high, while serum concentrations may be low, except in vernal conjunctivitis (indicating systemic and local response).

It is important to be able to detect local allergic reactions so that they can be used to distinguish locally produced allergic conjunctivitis.31-33 Measurement of serum IgE concentrations does not differentiate between local and systemic levels.30 Lipid disruption due to arachidonic acid formed by the allergic cascade affects tear fluid evaporation. This means that allergic eye can mask itself as a presenting dry eye.

IgE (anaphylactic) ocular responses include the following forms of conjunctivitis: GAC (General Allergic), SAC (Seasonal Allergic), PAC (Perennial Allergic), AKC (Atopic), GPC (Giant Papillary) and VKC (Vernal). Previously, the diagnosis of allergic conjunctivitis was based mainly on clinical features, particularly itching, and hyperemia or the presence of conjunctival papillae. There was no specific diagnostic technique that could be used reliably to confirm the presence of allergic conjunctivitis.18 Eosinophils in conjunctival scrapings are helpful in confirming the diagnosis,19-24 but positive detection rates (45%) are not very high.25,26,27

Several authors have developed comparison charts of signs and symptoms associated with various ocular disease states such as allergic, atopic, microbial, vernal etc.39-42 These comparisons confirm that redness and/or itching are not exclusively associated with allergic conjunctivitis. Clinical studies have demonstrated that traditional "Signs and Symptoms" are statistically unreliable markers for the clinical diagnosis of the allergic eye.

However, when using IgE values, allergic inflammation was clearly distinguished from bacterial and viral inflammation. While there was no statistical difference between normals and bacterial and viral patients, elevations of IgE values indicate either an ocular allergy, or an allergic component of the inflammatory response such as exotoxin (bacterial) or exfoliated necrotic tissue (viral).43

Concentrations of IgE are related to both the extent and the cumulative number of different allergens. Measurement of both eyes can aid in the differentiation of local responses versus systemic responses. Since this is a serious condition, patients with high IgE levels in both eyes should be considered for further systemic evaluation. Untreated allergic conjunctivitis or sub-acute responses are a risk factor for haze and regression after PRK45 and potential GPC when fitting contact lenses.34,36

Performance Characteristics

Sensitivity (>80 ng/ml): 93% (correctly ID allergic)
Specificity (<80 ng/ml): 96% (correctly ID non-allergic)
Accuracy: 95%
Precision: (at 200 ng/ml) >96% (maximum CV at 8 clinical sites = 4%).
Dynamic Range: 20 ng/ml to 2000 ng/ml.
Interactions -- No interference or cross-reaction was observed with the following concentrations of protein:

  Minimum
Assayed
Concentrations		 Maximum
Assayed
Concentrations		 Normal
Tear
Concentrations
IgA 0 mg/mL 2 mg/mL 1.6 mg/mL
IgG 0 ug/mL 2 mg/mL 0.02 pg/mL
Lactoferrin 0 mg/mL 2 mg/mL 1.5 mg/mL
Lysozyme 0 mg/mL 2 mg/mL 1.2 mg/mL
Human albumin 0 mg/mL 5 mg/mL 3.9 mg/mL

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