[Comparison of intradermal and prick tests based on samples of the most common allergens in the Zadar region]

The practical clinical problem of evaluating the significance of positive dermal tests is present in daily in vivo diagnoses in allergology and clinical immunology. Our research was aimed at a comparison of the two methods of dermal tests, namely, intradermal (i.d.) and prick tests, based on a sample of the most common allergenics in the Zadar region. The intradermal method was applied to a group of 664 patients, the prick test was used in a group of 641 patients, and 60 patients were examined using both methods. In the tests allergens from extracts of Dermatophagoides pteronyssinus, tree, weeds and grass pollens, dust, feathers, eggs, milk, flour, meat and fish from the Zagreb Institute of Immunology were used. A solution of histamine chloride and buffer saline containing 50% glycerol, prepared by the same Institute was used as a control. We considered a positive reaction to the intradermal test to have occurred when an urticaria of 5 or more mm radius with surrounding inflammation developed. A reaction to the prick method was considered to have taken place when an urticaria of 3 or more mm radius, together with surrounding inflammation resulted. A positive reaction was shown in 30% of those to whom the prick test was applied, and in 32% of those to whom intradermal tests were used, which represents 0.11-0.13% of the total adult population of the region of Zadar. A positive reaction to a single allergen was shown in 43% of the patients tested by i.d. test, and in 52% of the patients tested with the prick method. The most common oversensitivity with both methods was shown to Dermatophagoides pteronyssinus (86% i.d., and 56% prick, respectively). Among the pollen allergenics the most common reaction was to grass pollen (47% i.d., 65% prick). With patients who were tested with both methods (60 patients), there were also differences in results. An equal dermal reaction to both tests was shown in 32% of the patients, minor differences were present in 45%, and significant differences occurred with 23% of the patients. Regarding Dermatophagoides pteronyssinus, it is shown that the positive dermal reaction was statistically significantly larger with patients tested with i.d. than when the prick test was used (chi 2 = 17.39, p < 0.05). There was no statistically significant difference between the two methods regarding the allergenics of pollen and feather. These results lead to the conclusion that it is necessary to uniform the conditions for allergological tests. This implies the use of standardized allergenic preparations of similar concentrations, the selection of a uniform method and technique for testing, and compliance with other relevant factors.