This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
Positive Schick's test indicates that person is: 
Select and explain. 
A. Immune to diphtheria, B. Hypersensitive to diptheria, C. Susceptible to diphtheria, D. Carrier of diptheria
C: Susceptible to diphtheria
Answer: C: Susceptible to diphtheria 
Explanation: Positive Schick's test indicates that person is Susceptible to diphtheria. Schick test: Toxin-antitoxin neutralization test. Done on the people before staing immunization to identify susceptible individuals. Susceptible individuals develop erythema and induration on test arm following intradermal inoculation (0.2ml I/D MLD) of toxin. Vaccine is administered only to those susceptible people. Since now safer toxoid preparations are available, it is obsolete.