What this test measures
The Widal tube agglutination test is the quantitative version of the slide Widal. Serial dilutions of the patient's serum are mixed with O, H and paratyphoid antigens in test tubes and incubated. The highest dilution at which agglutination is still visible defines the antibody titre (e.g. 1:80, 1:160, 1:320, 1:640).
The tube method gives a more precise titre than the slide method and is the traditional reference Widal procedure. Like the slide Widal, it is supportive — not definitive — for typhoid diagnosis, and its interpretation requires knowledge of baseline antibody levels in the local population (which is high in endemic India).
Why it matters
A precise titre is more useful than a yes/no result when the same patient can be sampled twice — acute serum (week 1) and convalescent serum (week 2–3). A 4-fold rise in titres between the two samples is the most reliable Widal-based criterion for current typhoid infection. In practice, this paired sampling is rarely done in India because patients have already started antibiotics by the time the second sample is due.
For a single titre, an O titre ≥ 1:160 or H titre ≥ 1:320 in a febrile patient supports (but does not confirm) typhoid in many Indian guidelines. Blood culture remains the gold standard, especially with India's rising rates of antibiotic-resistant typhoid where culture-guided treatment is critical.
How to prepare
No fasting required. Best taken from day 5–7 of fever onwards. If paired sampling is planned, mark the date of the first sample so the second is taken 7–10 days later. Blood culture should ideally be sent before any antibiotic is started.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Salmonella Typhi O (TO) titre (—)[1] | Typically < 1:80 in Indian endemic populations | — | A single titre ≥ 1:160 in a clinically compatible illness supports typhoid. Confirm with a 4-fold rise in convalescent sample or with blood culture. |
| Salmonella Typhi H (TH) titre (—)[1] | Typically < 1:160 in Indian endemic populations | — | H titres rise later and persist for months to years after infection or vaccination. A persistently high H without rising O may reflect remote infection rather than current disease. |
| Paratyphi AH / BH titre (—)[1] | Typically low / negative | — | Raised AH or BH titres suggest paratyphoid A or B infection. Clinical illness and treatment overlap with typhoid; confirm with culture. |
Single vs paired Widal titre — what helps
| Scenario | Interpretation |
|---|---|
| Single low titre (<1:80) in week 1 | Inconclusive — antibody may not yet have risen |
| Single high TO ≥1:160 in clinical typhoid | Supports diagnosis, not definitive |
| Persistently high TH alone | Likely past infection or vaccination, not current |
| 4-fold rise between paired samples | Most reliable Widal criterion for current infection |
| Any Widal result + positive blood culture | Confirmed typhoid |
Frequently asked questions
How is tube Widal different from slide Widal?
The tube format gives a more precise quantitative titre (1:80, 1:160, 1:320 …), while the slide is a faster qualitative or semi-quantitative version. Tube is the traditional reference Widal procedure.
Is a high titre enough to diagnose typhoid?
No — particularly in endemic India where baseline titres are often raised. A high titre supports the diagnosis only when matched to a compatible clinical illness, and ideally backed by a 4-fold rise on paired sampling or a positive blood culture.
Do I really need to come back for a second sample?
Paired sampling 7–10 days apart is the most reliable Widal-based diagnostic criterion, but in practice many patients have started antibiotics and felt better by then. A blood culture taken early often makes the second Widal sample unnecessary.
I was vaccinated against typhoid — will my titres be high forever?
Vaccine-induced titres can persist for many months. Mention recent vaccination so your doctor can interpret a raised titre correctly.
Can the tube Widal replace blood culture?
No. Blood culture is the gold standard for typhoid and is the only test that tells your doctor which antibiotic will work — increasingly important in India where drug resistance is common.
How fast does the report come?
Tube Widal typically takes 4–24 hours depending on the lab's incubation protocol. Most NABL-accredited Mumbai and Thane labs deliver next-morning reports.
Is there a charge difference between tube and slide Widal?
The tube version is slightly more expensive because it uses more reagent and incubator time. Both are inexpensive compared to a blood culture.
Related Infectious Disease tests
Tests commonly ordered alongside WIDAL TUBE AGGLUTINATION, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Typhoid Fever · accessed 2026-05-30T00:00:00.000Z
- WHO — Typhoid Fever Fact Sheet · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Typhoid Fever · accessed 2026-05-30T00:00:00.000Z
- Indian Journal of Medical Microbiology — Widal in endemic settings · accessed 2026-05-30T00:00:00.000Z
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