Calibration' of our patch test reading technique is necessary

Background. Patch testing has been used for more than 100 years as the best means to diagnose contact allergy. The increased use of the technique makes standardization of the methodology most important. Progress in the standardization of the patch test technique has been made through guidelines. Objectives. To investigate the intra-individual and inter-individual differences in reading of patch tests in order to validate the actual patch test reading when reading is performed according to the same guidelines, and to determine whether information on guidelines actually improves the outcome of the patch test readings Patients/materials/methods. A patch test course for dermatologists was performed. Volunteers were patch tested with irritants and allergens in different concentrations. The patch test reader did not know what substances had been tested. Results. Irritant reactions/doubtful reactions and weak allergic reactions are difficult to differentiate (accordance for these reactions 21%, 19%, and 44%). Information and education have a beneficial effect on results, as shown by an improved kappa value. Conclusions. Standardization of patch test reading is important. Information on the classification system resulted in a significant improvement. Interpretation of guidelines should be continuously evaluated.