Skin Prick Tests and Enzyme-Linked Immunosorbent Assays among Allergic Patients Using Allergenic Local Pollen Extracts.

Abstract

Background: Allergic respiratory diseases are prevalent in the Philippines, with allergic rhinitis and asthma occurring at 20% and 8.7% of the population, respectively. The diagnosis of respiratory allergies is achieved by a combination of patient history and different screening tools, especially for the identification of the allergic triggers such as allergy skin prick test (SPT) and serum-specific IgE enzyme-linked immunosorbent assays (sIgE ELISA). The Philippines, being a tropical country, have a wide variety of plant species with potential to produce allergenic pollen grains. Knowledge of the sensitization profiles of Filipino allergic patients to our local pollen allergens is currently limited.

Objectives: The aim of this study is to determine the sensitization profile of patients with respiratory allergies (allergic rhinitis and/or asthma) through the allergy skin prick test (SPT) using allergenic local pollen extracts. It also aimed to determine if there is a positive agreement between the SPT and sIgE ELISA positivity rate and whether the results have relationship with the pollen purity and the protein content of the extracts.

Methods: Pollen allergens were extracted from Amaranthus spinosus (pigweed), Mimosa pudica (makahiya), Tridax procumbens (wild daisy), Imperata cylindrica (cogon), Oryza sativa (rice), Pennisetum polystachion (foxtail grass), Sorghum halepense (Johnson grass), Albizia saman (acacia), Cocos nucifera (coconut), Leucaena leucocephala (ipil-ipil), and Mangifera indica (mango). SPT was performed at the Allergy Clinic of the University of the Philippines-Philippine General Hospital on patients with allergic rhinitis and/or bronchial asthma. Blood samples were collected from patients who developed wheal diameters of 3 mm or more than the negative control. Sera were tested against the same pollen extracts using ELISA.

Results: Of the one hundred sixty-five (165) patients who submitted for skin prick test, 129 showed positive SPT results to the pollen extracts. Weeds were the most sensitizing (51.9%-58.1%). Blood samples were collected from these patients and tested for sIgE ELISA and among them, 71 were positive in the sIgE ELISA. Highest sensitization rates in sIgE ELISA were found in coconut, pigweed, Johnson grass, and rice. The highest positive agreements or the proportion of patients with positive sIgE ELISA among those with positive SPT were in coconut, followed by Johnson grass, pigweed, and rice. Most of the pollen sensitized patients on SPT are polysensitized.

Conclusion: SPT is a safe, simple, and rapid method for the diagnosis of IgE-mediated allergy. The lower number of positive patients in sIgE ELISA may be attributed to the low serum IgE levels and low quantities of effectual allergen components in extracts. Results of both SPT and ELISA must be correlated with a patient's clinical history, particularly the patient's exposures, and physical examination.