Audit of Finn Chamber patch test preparation

Reproducibility of patch test reactions is an important aspect of patch testing. Thin layer rapid use epicutaneous tests (TRUE Test) are preloaded with allergen, whereas Finn Chambers are empty discs that have allergen applied from a syringe. The amount of allergen applied to each Finn Chamber is therefore potentially variable depending on technique. This may increase the risk of non-reproducibility of reactions. We have performed an audit of patch test preparation in our department looking at weight variation of both individual Finn Chambers and 3 completed panels before and after allergen application. We found that the variance in weight was not significant for 2 of the 3 panels and single Finn Chambers with allergen in petrolatum. The variance in weight was significant for single Finn Chambers with allergen in solution and the third panel, which contains an allergen in solution. The clinical significance of these results is unclear.