Positive shick’s test indicates that person is :
So, the core concept here is the Shick's test's role in assessing immunity. The test uses a small amount of diphtheria toxin. If the person has sufficient antitoxin (from vaccination or prior infection), there won't be a reaction. If there's a reaction, like redness and swelling, it means they lack enough antitoxin and are susceptible.
The correct answer should be that a positive Shick's test indicates susceptibility. The options might include things like immunity, carrier status, or other conditions. Let me think about the possible wrong options. Common mistakes could be confusing it with a carrier test or thinking it indicates immunity. Also, maybe someone might confuse it with a test for another disease like tetanus.
For each incorrect option, I need to explain why it's wrong. For example, if an option says "immune," that's incorrect because a positive test shows lack of immunity. Another option might be "carrier," but the Shick's test doesn't detect carriers; it checks for antitoxin levels. Other diseases like tetanus use different tests, so those options are also incorrect.
The clinical pearl here is that a positive Shick's test means the person is not immune and needs vaccination. It's important to remember that this test is historical now, as routine vaccination has made diphtheria rare in many places. But for exams, knowing the test's purpose is key.
Wait, the user didn't provide the options. But the correct answer given is that a positive test indicates susceptibility. So the correct answer is that the person is susceptible. Let me structure the explanation accordingly, making sure to cover each section as per the user's instructions.
**Core Concept**
The Shick test is a diagnostic tool used to determine susceptibility to *Corynebacterium diphtheriae* by measuring the presence of diphtheria antitoxin in the blood. A positive result indicates insufficient antitoxin to neutralize a small dose of diphtheria toxin, confirming the individual is **not immune** to diphtheria.
**Why the Correct Answer is Right**
A positive Shick test (redness/swelling at the injection site) occurs when there is **no pre-existing antitoxin** to bind and neutralize the diphtheria toxin administered in the test. This confirms the person is **susceptible** to diphtheria infection and requires immunization. The test relies on the toxin-antitoxin neutralization principle: antitoxin (IgG antibodies) binds to diphtheria toxin, preventing cellular damage and the local inflammatory reaction observed in susceptible individuals.
**Why Each Wrong Option is Incorrect**
**Option A:** *Immune* – Incorrect. A negative Shick test (no reaction) indicates immunity, not a positive result.
**Option B:** *Carrier* – Incorrect. The Shick test does not detect carriers of *C. diphtheriae*; it assesses antitox