THE SKIN-TEST-SCANNER (STS) - A SCANNING SYSTEM FOR OBJECTIVE MEASUREMENT OF SKIN-TEST REACTIONS

Skin tests are widely used in the diagnosis of allergic diseases. The most common way to evaluate the degree of sensitization with skin test ing is either to compare the size of the allergen-induced wheal with a histamine reference wheal, or to quantitate the wheal area by measuri ng wheal parameters such as midpoint orthogonal diameter and area calc ulation. We evaluated a new objective method based on a laser-scanning system (Skin-Test-Scanner: STS). To test the calibration of the syste m, we scanned exactly defined reference areas. We also investigated th e intraoperator reproducibility of the STS in comparison with current techniques used in the estimation of skin test wheal areas in clinical practice. For the calibration of STS we found deviations from the giv en area depending on the square measure between 4.03 +/-: 3.62% (3 mm( 2)) and 0.55 +/- 0.92% (50 mm(2)). In the range most important for the determination of skin test results, deviations were 2.70 +/- 3.45% (5 mm(2)), 2.93 +/- 3.45% (10 mm(2)) and 1.93 +/- 4.31% (30 mm(2)). No s ignificant differences were found when comparing intra- and inter-exam iner Variability of the system. In clinical applications, STS had sign ificantly better reproducable results when compared to the diameter me thod (p less than or equal to 0,05, Wilcoxon).