COMPARATIVE PERFORMANCE OF 5 COMMERCIAL PRICK SKIN-TEST DEVICES

Five commercially available devices for performing prick skin testing were compared for reproducibility, patient acceptance, occurrence of false-negative skin test results, and size distribution of reactions at the negative control sites. Reproducibility of skin testing with 10 mg/ml histamine base, as expressed by coefficient of variation, was similar. However a clear range of trauma to the skin was produced by the devices. This trauma was least with the Hollister-Stier and ALK Laboratories lancets, intermediate for the bifurcated needle by either prick or puncture, and greatest for the Multi-Test and DermaPIK devices. The more traumatic devices produced larger mean wheals and more frequent and large reactions at saline control sites, and were less acceptable to subjects. However, except for the Multi- Test device, they less often yielded false-negative responses. It is proposed that for each device a different size of wheal must be produced at the allergen site to have confidence that it exceeds the control site. The wheal size necessary for 99% specificity were as follows: Hollister-Stier lancet, 2 mm; ALK lancet, 3.0 mm; bifurcated needle prick, 4.0 mm; bifurcated needle puncture, 4.5 mm; Multi-Test device, 5.0 mm; and DermaPIK device, 5.5 mm. An additional observation was the presence of a significant gradient of reaction size on the back to both histamine and allergen (p < 0.0001), with the smallest reactions in the upper third and the largest in the lower third of the back.