Question

Which one of the following is NOT true about enteric fever?

• A. Blood culture is diagnostic
• B. Bone marrow cultures are positive in the second week
• C. Widal test is diagnostic at 7th day
• D. Four fold rise in Widal titre is an indication of enteric fever

Hint:

Look closely at which single Widal statement overstates what one test result can prove.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks which statement about enteric fever (typhoid) is FALSE.

Step 2: Key Concept or Approach:
Diagnosis of enteric fever relies on blood culture in the first week, bone marrow culture (which stays positive later into the illness, even after antibiotics), and serology like the Widal test, which detects antibodies against Salmonella O and H antigens. A single Widal titre can be misleading because of baseline antibody levels in an endemic population, so one reading is not considered diagnostic; a fourfold or greater rise in titre between acute and convalescent sera is what actually confirms the diagnosis.

Step 3: Working Through the Options:
Blood culture is diagnostic and remains the gold standard, especially in the first week of illness, so this statement is true. Bone marrow culture positivity extending into the second week is also a true and well-known fact, useful when blood culture is negative or the patient has already received antibiotics. A fourfold rise in Widal titre being an indicator of enteric fever is true and is the actual basis of interpreting the Widal test. Saying the Widal test is diagnostic at the 7th day is incorrect, because a single titre value on any given day cannot reliably confirm the diagnosis without a paired rising titre or an established local baseline.

Step 4: Conclusion:
The correct answer is that the Widal test is diagnostic at the 7th day, since this is the false statement among the options.