Experimental investigations in guinea pigs on the recognition of the allergic eczematous reaction: A comparison of the macrophage migration inhibition test with the patch test.

1. The patch test as an in vivo test has disadvantages. It is our impression that biologically false reactions occur in approximately 5%. 2. The MIT as an in vitro test is very time consuming, but safe for the patient. It is supposed to give up to 20% false reactions. 3. In 76 and 72% of 156 guinea pigs sensitized with potassium bichromate and sulfasol respectively, both the test methods gave results in agreement. 4. Sensitization by potassium bichromate estimated by patch test only was 30%, and by MIT only also 30%, but the two test methods disagreed in 24%. 5. Sensitization by sulfasol evaluated in the patch test only was 36%, and in the MIT only 48% but the two test methods disagreed in 28%. 6. The differences between the results of the two test methods are not satistically significant and their failure rate does not provide absolutely sure results, but we believe that the patch test is preferrable in recognition of contact allergy because it is in vivo and probably has a lower failure rate in comparison with the MIT in the human.