Determination of the Sensitivity and Specificity of Prick Test Betula Verrucosa

Extract Allergen From Betula Verrucosa. Test Sensitivity and Specificity of Diagnostic in Prick Test Preparation.

The main objective is to evaluate the concentration of allergen extract of Betula verrucosa that elicit a papule equivalent to that produced by a solution of histamine dihydrochloride 10 mg / ml in size.

Open, prospective, unblinded and non-randomized biological assay. Each patient was tested with four concentrations of allergen and with a histamine and saline solution as positive and negative controls, respectively.

General inclusion criteria for both groups:

• Positive skin prick test with the positive control (Histamine HCl at 10 mg/mL). The length of the largest diameter of the wheal induced by this control should be ≥ 3 mm.
• Negative skin prick test with the negative control. The length of the largest diameter of the wheal induced by this control should be < 3 mm.
• All ages and both genders.

For the group of patients CH+ (true positive to Betula verrucosa): All these patients had a previous diagnosis of allergy to the birch pollen:

• A positive case history with inhalant allergy related to exposure to birch pollen.
• A positive skin prick test (mean wheal diameter ≥ 3 mm) when tested with a biologically standardized extract prepared from birch pollen. This preparation, from another manufacturer, was the one used in the routine in the Hospital.
• Positive test for specific IgE (CAP value > 0.35 IU/mL). For the group of patients CH- (true negative to Betula verrucosa): All these patients had a previous diagnosis of allergy to agents unrelated to birch pollen.
• A negative case history with inhalant allergy related to exposure to birch pollen or to pollen with known cross-reactivity with the birch pollen. These patients could be allergic to other pollen or other allergens, such mites.
• A negative prick test (largest diameter of the wheal ≥ 3 mm) when tested with a standardized extract prepared from the allergen source in question.
• A negative test for specific IgE (CAP value < 0.35 IU/mL) to birch pollen or to pollen with known cross-reactivity with birch pollen: Corylus avellana, Quercus verrucosa, Fagus sylvatica, Castanea satavia, Carpinus betelus and Alnus glutinosa.

Exclusion criteria for both groups:

• Patients that were using drugs that may interfere with the skin prick tests.
• Patients using the following drugs 24 hours before the test: theophylline, systemic corticosteroids.
• Patients in which the largest diameter of the wheal induced by the positive control was < 3 mm.
• Patients in which the largest diameter of the wheal induced by the negative control was ≥ 3 mm.
• Pregnancy, dermographism, atopic dermatitis (locally at the test site), urticaria.
• Patients who suffer disease in which the use of adrenaline is not allowed.
• Patients with any severe psychiatric disease.

For the patients CH+:

• Patients that received or are treated with immunotherapy with an allergenic extract of birch pollen and/or with allergen extracts with known cross-reactivity to birch pollen (Corylus avellana, Quercus verrucosa, Fagus sylvatica, Castanea satavia, Carpinus betelus and Alnus glutinosa).

For the patients CH-:

• Patients sensitized to pollen with demonstrated cross-reactivity with the pollen of Betula verrucosa. These pollen included Corylus avellana, Quercus verrucosa, Fagus sylvatica, Castanea satavia, Carpinus betelus and Alnus glutinosa.