What does a positive schick test indicate?
Immune status of an individual to Corynebacterium diphtheria is assessed by the presence of antitoxin levels or schick test. This test is done by injecting 0.1ml of highly purified toxin into one forearm and 0.1ml of heat inactivated toxin into another forearm as a control. A positive reaction is characterized by a local inflammatory reaction that reaches maximum intensity in 4-7 days and reduces gradually. This indicates absence of immunity to C. diphtheriae. Negative reaction indicates presence of antitoxin in the individual which neutralizes the toxin injected. Such individuals are immune to C diphtheriae infection. Ref: Sherris Medical Microbiology By Kenneth J. Ryan, 5th Edition, Chapter 26 ; Textbook of Microbiology and Immunology By Parija, Page 224
Carrier of diphtheria
Immune to diphtheria
Susceptible to diphtheria
Hypersensitivity to diphtheria