Effect of test techniques on perfusion of neomycin sulfate patch tests - Acomparative study with visual assessments

Effects of test techniques on neomycin patch test results have not been tho roughly investigated. This study focuses on effects of dose and application rime of neomycin sulfate patch tests on test results. The effects are asse ssed both visually and by perfusion. 16 subjects positive to neomycin are r etested with neomycin sulfate in various doses and vehicles applied with di fferent application devices for variable time intervals. All subjects were tested with a serial-dose series for time intervals ranging from 3 to 96 h (4 days [D]). The results show very good agreement between perfusion assess ments and positive and negative visual assessments of reactions; however, a gray zone was detected where reactions with variable perfusion were associ ated with visually questionable test responses. 1:27 serial dilutions and w ide application time intervals show a positive response with perfusion asse ssments and partly with visual assessments. Regardless of reading technique , highest reactivity of reactions was detected at either 96 h (day [D] 4) o r 168 h (D7) in each subject with minor exceptions, regardless of dose, veh icle, application device or application time. Some findings of the study su pport the idea that reactions with papules alone are positive rests. Possib le effect of tapes and foils on test results are discussed. (C) Munksgaard, 2000.