The guinea pig maximization test--with a multiple dose design
The guinea pig maximization test (GPMT) is usually performed with one moderately irritant induction dose of the allergen and gives a qualitative assessment-hazard identification-of the allergenicity of the chemical. We refined the GPMT by applying a multiple dose design and used 30 guinea pigs in a test divided into a control group and 5 test groups of 5 animals. Each group was treated with different induction concentrations of the allergens: formaldehyde, cinnamic aldehyde, propyl paraben, lidocaine, mercaptobenzothiazole or chlormethylisothiazolinone/methylisothiazolinone. The test results were analysed using a logistic multidose response model. The precision of the results depends only on the total number of animals, the dose design and the response pattern. The maximal sensitization rate for a chemical was determined, and the intracutaneous induction concentration that sensitized 50% of the animals (EC50) (or another percentage) was estimated. Further studies are needed to prove the validity of this idea. However, improvements in protocols for the GPMT are needed to reduce interlaboratory variability in results and to reduce the number of animals used for allergenicity tests.