Results obtained with the Dick test in normal individuals and in acute and convalescent cases of scarlet fever.

Abstract

Studies have been made with the Dick test among normal individuals along lines similar to those carried out with the Schick test. The susceptibility by age groups from birth to adult life has been investigated and found to correspond closely to the percentage susceptibility to diphtheria, as shown by the Schick test. Comparative studies have been made with the reaction on mothers and their offspring. The results indicate that the reactions are similar in the mother and offspring during the first six months of life. The antibodies are transmitted through the placenta and persist in most infants for a period of about six to nine months. The blood sera of individuals who gave positive or negative Dick reactions have been studied for their properties in causing the extinction test of Schultz-Charlton in a fresh scarlet fever rash; also for their power to neutralize the test fluid for the Dick reaction.

The blood serum of a person giving a “negative” or a “pseudo” Dick reaction causes blanching of the rash and neutralizes the test toxin; that of a “positive or a combined” reaction causes no blanching of the rash and does not neutralize the test toxin. The Dick test is positive as a rule during the first two days of scarlet fever but becomes less positive toward the end of seven days and negative toward the end of ten to fifteen days, when the antitoxic properties begin to appear in the patient's serum. This can be shown by its power to blanch the scarlet fever rash and neutralize the Dick test toxin. The neutralization of the test toxin is a more delicate index of the presence of antibodies in a serum than its property to cause blanching of a scarlet fever rash.