Positive schick test indicates
**Core Concept**
The Schick test is a method used to determine an individual's susceptibility to diphtheria toxin. It involves injecting a small amount of diphtheria toxin into the skin and observing the reaction. The test is based on the principle that individuals with antibodies against diphtheria toxin will not develop a significant reaction, whereas those without antibodies will show a localized reaction.
**Why the Correct Answer is Right**
When a person is exposed to diphtheria toxin, their immune system produces antibodies against the toxin. These antibodies neutralize the toxin, preventing it from causing damage. In individuals who have been immunized against diphtheria, the Schick test will typically show a negative result, indicating that they have developed antibodies against the toxin. On the other hand, individuals who have not been immunized or have waning immunity will show a positive result, indicating that they are susceptible to diphtheria.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a correct description of the Schick test result. While it may seem plausible, it is not a direct indication of the test's outcome.
**Option B:** This option is incorrect because the Schick test is not used to diagnose diphtheria, but rather to assess an individual's susceptibility to the disease.
**Option C:** This option is not a correct interpretation of the Schick test result. The test is not directly related to the production of antibodies against tetanus toxin.
**Clinical Pearl / High-Yield Fact**
The Schick test is an important tool for determining an individual's susceptibility to diphtheria. It is especially useful in areas where diphtheria is prevalent or in individuals who have not received the necessary vaccinations.
**Correct Answer: C. Susceptibility to diphtheria toxin.**