The chemical test that is used for diagnosis of typhoid is:a)ESR-Testb)PCR-Testc)Widal-Testd)ELISA-TestCorrect answer is option 'C'. Can you explain this answer?

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The Widal test is one method that may be used to help make a presumptive diagnosis of enteric fever, also known as typhoid fever.The test was based on demonstrating the presence of agglutinin (antibody) in the serum of an infected patient, against the H (flagellar) and O (somatic) antigens ofSalmonella typhi.

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(C)widal test is right answer this is given in NCERT and docs

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Widal test is right it is given in many books including ncert

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Widal test

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C

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For typhoid - Widal test

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C widal test in chapter human health and disease we have studied it

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Widal test

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C

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Widal test

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Widal test is an agglutination test which detect the presence of serum agglutinins (h and o)  in patient serum with typhoid and para typhoid.

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Widal test

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Widal test

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Rammurti commit

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The Widal Test for Typhoid Diagnosis

The correct answer is option 'C', the Widal test. The Widal test is a serological test used for the diagnosis of typhoid fever caused by the bacterium Salmonella typhi. This test detects antibodies produced by the body in response to the infection.

How Does the Widal Test Work?

The Widal test is based on the principle of agglutination, which refers to the clumping together of particles. In this case, the test detects the agglutination of bacterial antigens with specific antibodies in the patient's serum.

When a person becomes infected with Salmonella typhi, their immune system produces antibodies against the bacteria. These antibodies include both IgM and IgG types. The Widal test measures the presence and levels of these antibodies in the patient's blood.

The Procedure of the Widal Test

The Widal test is performed using a tube agglutination method. The procedure involves the following steps:

1. Serum Collection: Blood samples are collected from the patient suspected of having typhoid fever.

2. Preparation of Antigens: Bacterial antigens of Salmonella typhi are prepared in the laboratory.

3. Serial Dilutions: The patient's serum is diluted in a series of tubes, and the bacterial antigens are added to each tube.

4. Observation for Agglutination: The tubes are observed for agglutination after incubation. If the patient's serum contains antibodies against Salmonella typhi, the bacteria will clump together, indicating a positive reaction.

Interpreting the Widal Test Results

The Widal test results are reported as the reciprocal of the highest dilution that shows agglutination. A titer of 1:160 or higher is considered significant for the diagnosis of typhoid fever. The presence of rising antibody titers in paired serum samples taken during the acute and convalescent stages of the illness further supports the diagnosis.

Limitations of the Widal Test

Although the Widal test is widely used, it has certain limitations. False positives can occur due to cross-reactivity with other bacterial infections or previous immunizations. False negatives may result if the test is performed too early in the course of the illness or if the patient has received antibiotics prior to testing.

Conclusion

The Widal test is a valuable tool for diagnosing typhoid fever. By detecting the presence of antibodies against Salmonella typhi, it helps in confirming the infection. However, it should be interpreted in conjunction with clinical symptoms, medical history, and additional laboratory tests for a more accurate diagnosis.

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