FaridabadBy Dr B.C. Gupta, MD · 2026-10-01
Ask the Pathologist - MCQ of the Week. A short question to test how well you know common laboratory tests, with a plain-English explanation from Dr B.C. Gupta, MD (Pathology).
Q. Which laboratory test grows the typhoid bacteria from a patient's blood and confirms the infection?
- A. Widal test
- B. Blood culture
- C. Complete blood count
- D. Dengue NS1
Answer: B. Blood culture
Blood culture is the test that actually grows Salmonella typhi from the sample. Because the bacteria are cultured and identified directly, a positive result confirms the infection rather than only suggesting it. It also gives a sensitivity report, which tells the doctor which antibiotics the organism responds to. Its main drawback is time: the culture usually needs two to three days before it can be reported.
The Widal test is the one people often confuse with a confirmatory test. Widal measures antibodies the body produces against the typhoid bacteria. Antibodies take several days to appear, and they can persist after an earlier infection or vaccination, so a single Widal titre can be misleading in either direction. It is a useful and quick test, but it is interpreted together with the timing of the fever and the patient's symptoms.
A complete blood count and a dengue NS1 do not detect typhoid at all. A CBC may show changes that support the clinical picture, and dengue NS1 is used when dengue is suspected. If your doctor has asked for a blood culture or a Widal test, call the centre to confirm preparation and timing before you visit.
