Introduction: Skin tests are the most useful single modality for demonstrating an IgE-mediated mechanism underlying clinical symptoms. Skin reactivity to an allergen depends on person's exposure and genetic factors influencing the IgE response. However, the reproducibility of allergy skin tests has been shown to be variable depending, among other things, on the allergen extract employed and the kind of technique used. These variations have led to controversy regarding clinical relevancy of allergy skin testing [1-7]. We examined the relationship of skin-prick test and serum allergen-specific IgE in pollen susceptible adult persons. We estimated changes in the immediate skin reactivity to pollen-allergens by testing patients on more than one occasion: a) during and out of pollen season; b) before and after completing specific immunotherapy, and c) who had been tested with diverse concentrations of the same pollen-allergen. We correlated the degree of skin reactivity at the initial and subsequent testings with the aim of estimate diagnostic relevancy of such performed allergy skin testings.
Material and methods: Study was performed in 64 persons (aged from 17 to 43 years) suffering from rhinitis or rhinoconjunctivitis or asthma. They were diagnosed for the first time [8, 9]. None of selected persons had proven dermographism [1, 9]. Study protocol Skin prick tests were performed according to recommended protocol reviewed elsewhere [9]. Blood samples for total and allergen-specific IgE were taken in the morning on the test-day and sera were stored until analyses. Testing was performed with in house standardized extract of grass pollens (each of 5000 AU/allergy unit per milliliter): Dactylis glomerata and Phleum pratense and Lolium perenne (produced by Torlak Institute, Belgrade). Testing was performed in selected groups of patients: a) during and out of pollen season; b) before and after allergen-specific immunotherapy, and c) with three diverse concentrations of Phleum pratense allergenic extract (5000 AU, 7500 AU and 10,000 AU/ml). During the study a medication was not allowed at least 7 days prior to the skin testing (14 days for hydroxyzine). Alergen-specific IgE in serum (RAST) Determination of serum allergen-specific IgE was performed by using commercially available Pharmacia kit (EIA RAST Phadesim). For allergen-specific IgE results were expressed in classes (1 minimal to 4-maximal concentrations) determined by manufacturer. Study was performed under approval of the Ethic Committee of our hospital. For statistical analysis we used t-test and test of variance (ANOVA). Results were considered significant if p < 0.05.
Results: Influence of allergen-specific serum IgE concentration on local skin reactivity was estimated in 23 persons (17 females, 6 males), and is shown in Table 1. The largest papule diameter was registered in high susceptible persons (RAST class 4). Influences of season when testing was performed and specific immunotherapy were estimated in 26 persons (19 females, 7 males) (Figures 1 and 2). The effect of diverse allergenic extract concentrations was estimated in 15 adults (9 females, 6 males, mean age 26.4 years) and results are shown in Figure 3.
Discussion: In the study it has been shown that serum concentration of allergen-specific IgE positively correlated with the skin reactivity to pollen-extract. In addition, allergen specific immunotherapy as well as the concentrations of the used allergenic extract influenced significantly local skin reactivity. On the contrary, season when testing had no influence. According to our results, it seems that skin reactions (papule), equal or larger than 6 mm in diameter, could be of diagnostic value concerning pollen-monotest application (Table 1). Meanwhile, with significance of 95% we could postulate that in persons tested with the lowest concentration of allergen-solution (5000 AU/ml), skin prick reactivity defined by the papule of 4 mm or larger can replace in vitro