Comparative performance of five 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.

Immediate skin test reactivity to Food and Drug Administration-approved standardized extracts.

In an effort to determine whether recently introduced Food and Drug Administration-approved standardized extracts produce clinically appropriate responses in a population, 200 subjects were skin prick tested (SPT). Thirteen extracts (10 pollens, two house dust (HD) mites and cat) were tested in three groups of subjects, 50 with a history of asthma or allergic rhinitis (AL), 50 without asthma or perennial or seasonal allergic rhinitis but with a positive immediate family history for these conditions (FAL), and 100 subjects without a personal or family history for these conditions (NAL). An SPT mean wheal diameter greater than or equal to 3 mm was considered positive. Ninety percent (95% confidence interval [CI], 82% to 98%) of AL subjects had at least one positive SPT. Forty-six percent of FAL subjects (95% CI, 30% to 58%) and 29% of NAL subjects (95% CI, 20% to 38%) had at least one positive SPT. More FAL than NAL subjects had at least one SPT (p less than 0.05), and FAL subjects had more positive SPTs than NAL subjects (p less than 0.05), further supporting the genetic regulation of allergen-specific IgE production. Of the five AL subjects with no SPT wheal greater than or equal to 3 mm, three subjects were available for intradermal tests. Thirteen nonstandardized allergens similar to allergens used for SPT were applied intradermally in each of these three subjects and were all negative. Compared with history, an SPT wheal greater than or equal to 3 mm to cat produced a sensitivity of 0.90, a specificity of 0.90, and diagnostic accuracy of 0.90. Tenfold dilutions of pollens and cat reduced sensitivity without significantly improving specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of six epicutaneous devices in the performance of immediate hypersensitivity skin testing.

Six devices commonly used for immediate hypersensitivity epicutaneous skin testing were compared with regard to precision and diagnostic accuracy. Fifteen subjects were tested on the back to 10 mg/ml of histamine phosphate and 50% glycerosaline by prick technique with a smallpox needle (SN), bifurcated needle (BN), Greer "pen" (GP), and blood lancet, and by puncture with the Morrow-Brown needle (MB) and Multi-Test (MT). Five devices were tested in quintuplicate to histamine and once to glycerosaline in each subject; with MT, five histamine and three glycerosaline sites were used. Analysis of the wheal areas obtained with SN, BN, GP, and MB demonstrated comparable degrees of precision (coefficient of variation). The precision of MT was less than the other devices (p less than 0.05). The blood lancet demonstrated intermediate precision. Twenty-two of 45 (49%) of the glycerosaline skin tests performed with MT were falsely positive, significantly more than the other devices (p = 0.0001). We conclude that MB, BN, GP, and SP are comparable devices for use in immediate hypersensitivity skin testing. The low precision and reliability of MT used for testing on the back would appear to make this device less than adequate for diagnostic or research studies. Its high rate of false positive reactions requires caution in interpretation of results when it is used in the clinical diagnosis of allergy.