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Visual and laser Doppler perfusion scanning assessments of Kathon CG patch test reactions
1Department of Dermatology, Karolinska Hospital, Stockholm, Sweden and the National Institute for Working Life, Solna, Sweden.
Background:
Testing procedure for Kathon CG (Diagnostics AB, Tygelsjö, Sweden) is not standardized.
Objective:
To improve test results for Kathon CG.
Methods:
Eleven subjects were tested with Kathon CG patch tests applied from 6 to 96 hours. Tests were read visually and by a laser Doppler perfusion scanning technique at time points ranging from 6 to 240 hours.
Results:
There were large differences in the perfusion profiles of subjects tested in identical fashion. Beginning reactions were detected earlier with the laser Doppler scanning than with the visual assessment technique. There was no obvious agreement between peak perfusion values of reactions and application times. Both assessment techniques were effective at distinguishing between positive and negative subjects at an adequate dose and application time. This distinction was possible using a shorter reading time with the laser Doppler scanning for all subjects. Six-hour applications were sufficient to detect all positive subjects so tested regardless of assessment technique. With that application time, positive and negative subjects were most effectively identified using long reading times regardless of assessment technique.
Conclusion:
The shortest application time used on all subjects, 24 hours, was effective and 6-hour applications with long reading times for all subjects so tested. Doses lower than 0.0040 mg/cm2 resulted in false-negative tests.