Infections & SerologyNo Fasting RequiredTurnaround: 4–8 hours (same day)

Widal Test & Typhidot (Enteric / Typhoid Fever)

Also known as: Widal Agglutination Test, Typhidot Test, Enteric Fever Screen, Salmonella Serology

Parameters Measured in the Report

A breakdown of individual biomarkers and biological reference intervals typically found in your report:

Biomarker	Standard Range	Unit	What It Means
S. Typhi O Antigen Titer (TO Titer)	Normal: < 1:80 Clinically Significant: ≥ 1:160	titer ratio	Somatic bacterial surface antibody; significant titer suggests acute active enteric infection.
S. Typhi H Antigen Titer (TH Titer)	Normal: < 1:80 Clinically Significant: ≥ 1:160	titer ratio	Flagellar antibody; develops later and persists for months post-infection or post-vaccination.

* Note: Reference ranges may vary slightly between testing instruments and reagent kits. Always refer to the reference interval printed on your specific pathology report.

Clinical Focus

Serum agglutinating antibody titers against Salmonella enterica serovar Typhi O (somatic) and H (flagellar) antigens.

Sample & Specimen

Venous blood (Serum tube)

Fasting Protocol

No fasting required. Drink water normally before blood draw.

Turnaround Time

4–8 hours (same day)

What Is This Test?

The Widal Test is a classic tube agglutination serology test designed to detect antibodies against *Salmonella enterica* serovar Typhi, the bacterial pathogen responsible for Typhoid (Enteric) Fever, transmitted through contaminated food and water. When infected, the immune system develops antibodies against the bacterial surface **O (Somatic)** antigen (indicating acute active infection) and the **H (Flagellar)** antigen (which develops later and indicates past infection, vaccination, or convalescence). A fourfold rise in titer over 7 to 10 days provides definitive serological confirmation.

Why Did Your Doctor Order This Test?

Physicians routinely prescribe the Typhoid / Widal in the following clinical scenarios:

Prolonged continuous fever lasting more than 5 to 7 days, classically following a rising "step-ladder" pattern

Headache, malaise, dry cough, abdominal discomfort, coated tongue, constipation (in adults) or diarrhea (in children)

Hepatosplenomegaly (enlarged liver/spleen) or faint salmon-pink "rose spots" on the trunk

Relative bradycardia (pulse rate slower than expected for the degree of high fever, Faget sign)

How to Prepare Before Your Test

Fasting Requirement: No fasting required. Drink water normally before blood draw.

No fasting or special preparation required.

Understanding Your Results

What higher or lower readings generally mean in clinical practice:

If Values Are Higher Than Normal

A baseline S. Typhi O titer of ≥1:160 or a fourfold rise in paired samples taken 7–10 days apart supports the clinical diagnosis of Typhoid Fever. In endemic areas, baseline titers in healthy individuals can be 1:40–1:80 due to past subclinical exposure.

If Values Are Lower Than Normal

Titer ratios below 1:80 in the first week of fever do not rule out typhoid, as antibodies take 7 to 10 days to rise. Blood culture remains the gold standard definitive diagnostic during week 1.

Frequently Asked Questions

Why can the Widal test give false positive results?

Because the Widal test detects antibodies rather than the bacteria itself, prior typhoid vaccination, past treated infections, or cross-reacting non-typhoidal salmonella can cause positive titers. Doctors correlate titers with clinical symptoms.

Related Laboratory Tests

Tests frequently prescribed together or used as follow-up investigations:

Complete Blood Count (CBC / Hemogram)

Counts and evaluates red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.

Liver Function Test (LFT / Hepatic Panel)

Bilirubin fractions, transaminases (ALT/SGPT, AST/SGOT), Alkaline Phosphatase (ALP), and proteins (Albumin, Globulin).

Dengue Serology (NS1 Antigen, IgM & IgG)

Dengue virus non-structural protein 1 (NS1) antigen and host-produced IgM and IgG immunoglobulins.

Stool Routine & Occult Blood Examination (FOBT / R/M)

Microscopic presence of hidden (occult) hemoglobin, intestinal pus cells, red blood cells, ova, cysts, and parasites.

Medical & Diagnostic Disclaimer

This guide is published for educational and patient informational purposes only. It is not a substitute for professional medical evaluation, diagnosis, or clinical advice.

A laboratory result that falls slightly outside standard statistical reference intervals does not automatically indicate disease; conversely, a normal result does not guarantee the absence of medical conditions. Only your attending physician can interpret lab findings in the context of your medical history, physical exam, and symptoms.