The chemical test that is used for diagnosis of typhoid is

Options

A. ELISA- Test
B. ESR- Test
C. PCR- Test
D. Widal -Test.

Answer

To answer the question regarding the chemical test used for the diagnosis of typhoid, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Question**: The question asks for the chemical test used to diagnose typhoid.

2. **Review the Options**: The options provided are:
- A) ELISA test
- B) ESR test
- C) PCR test
- D) Vidal test

3. **Analyze Each Option**:
- **Option A: ELISA test**: This test stands for Enzyme-Linked Immunosorbent Assay and is primarily used for diagnosing infections like AIDS, not typhoid.
- **Option B: ESR test**: The Erythrocyte Sedimentation Rate (ESR) test measures the rate at which red blood cells settle in a tube of blood. It is not specific for typhoid diagnosis.
- **Option C: PCR test**: Polymerase Chain Reaction (PCR) is a technique used to amplify DNA segments. While it can be used in various diagnostics, it is not the standard test for typhoid.
- **Option D: Vidal test**: The Vidal test is specifically used for the diagnosis of typhoid fever by detecting the presence of antibodies against Salmonella typhi.

4. **Select the Correct Answer**: Based on the analysis, the correct answer is **Option D: Vidal test**.

5. **Conclusion**: The chemical test used for the diagnosis of typhoid is the Vidal test.

### Final Answer:
The chemical test that is used for the diagnosis of typhoid is the **Vidal test** (Option D).

---