Comparison of the sensitivities of the Buehler test and the guinea pig maximization test for predictive testing of contact allergy.

International test guidelines, such as the Organisation for Economic Cooperation and Development (OECD) guideline #406, recommend 2 guinea pig methods for testing of the contact allergenic potential of chemicals: the Guinea Pig Maximization Test (GPMT) and the Buehler test. Previous comparisons between the methods suggested that the Buehler test was less sensitive than the GPMT although modified Buehler test protocols were used. Parallel GPMT and Buehler tests were conducted according to OECD guideline #406 using a multiple-dose design and test results were analysed using a standard logistic dose-response model. To compare the sensitivity of the 2 test procedures the test conditions were kept identical and the following chemicals with a range of sensitization potentials were tested: chloraniline, chlorhexidine, eugenol, formaldehyde, mercaptobenzothiazole and neomycin sulphate. Formaldehyde and neomycin sulphate were strong sensitizers in both tests. Mercaptobenzothiazole, eugenol and chloraniline were all strong sensitizers in the GPMT, eugenol and mercaptobenzothiazole were negative in the Buehler test and equivocal results were obtained with chloraniline. Chlorhexidine was negative in the GPMT and equivocal responses were obtained with the Buehler test. Higher induction concentrations were needed to show allergenicity in the Buehler test and for some allergens the Buehler test protocol was not sensitive enough to demonstrate allergenic potential.