Tests of chicken pox-a) FAMAb) ELISAc) Widald) PCR
**Core Concept**
Varicella-zoster virus (VZV), the causative agent of chickenpox, requires laboratory testing for diagnosis and confirmation. These tests aim to detect the presence of VZV-specific antibodies, antigens, or genetic material.
**Why the Correct Answer is Right**
The correct answer is **Widal test**. The Widal test is a serological test used to detect the presence of antibodies against the **O** and **H** antigens of Salmonella Typhi, which causes typhoid fever. However, it can also be used to diagnose other infections, including paratyphoid fever, caused by Salmonella Paratyphi A and B. The Widal test is not specific for VZV but can be used to rule out other infections in patients presenting with fever and rash, making it a useful screening tool in clinical practice.
**Why Each Wrong Option is Incorrect**
* **Option A: FAMA** - FAMA is not a recognized test for diagnosing chickenpox.
* **Option B: ELISA** - While ELISA is a widely used serological test, it is not the primary test for diagnosing chickenpox. ELISA can be used to detect VZV-specific antibodies, but other tests like PCR and viral culture are more specific.
* **Option D: PCR** - PCR is a molecular test used to detect the genetic material of VZV, but it is not the most commonly used test for diagnosing chickenpox in clinical practice.
**Clinical Pearl / High-Yield Fact**
The Widal test is a useful screening tool in patients presenting with fever and rash, helping to rule out other infections like typhoid fever.
**Correct Answer:** C.