Apollo Diagnostics | NABL-Certified Lab | No Fasting Required | Priority Home Collection During Fever
What is a Widal Test?
The Widal Test is a serological diagnostic tool used to detect enteric fever — commonly known as typhoid and paratyphoid fever. These infections are caused by Salmonella typhi and Salmonella paratyphi bacteria, typically spread through contaminated food and water. The Widal test identifies specific antibodies in your blood that react to the O (somatic) and H (flagellar) antigens of these bacteria. When these antibodies are present they cause visible clumping (agglutination) on the test slide, helping doctors confirm whether persistent fever is due to typhoid.
⚠ Important: The Widal test is most reliable after the first week of continuous fever — the body needs 7–10 days to produce measurable antibody levels. A negative Widal in the first 5 days of fever does not rule out typhoid. No fasting is required. Always interpret Widal results alongside clinical symptoms and CBC, as high titers can occur in endemic populations without active infection.
Clinical Significance of O and H Antigens
A standard Widal report includes four parameters. Understanding the pattern is key to accurate interpretation:
- S. Typhi O (Somatic Antigen) — elevated O antibodies indicate active or recent typhoid infection. O antibodies appear early in the disease and decline faster after recovery.
- S. Typhi H (Flagellar Antigen) — elevated H antibodies can suggest a later stage of infection, past infection or prior typhoid vaccination. H antibodies persist longer after infection.
- S. Paratyphi AH & BH — detect paratyphoid fever Type A and Type B, which are generally milder than typhoid but require similar antibiotic treatment.
- Titer values — a titer of 1:160 or higher is generally considered clinically significant for active infection in endemic regions like Kolkata. Single titers should be interpreted with caution; a 4-fold rise in titer between two samples taken 7–14 days apart is more diagnostically conclusive.
Interpreting Widal Titer Results
| Titer Level | Interpretation |
|---|---|
| Below 1:80 | Normal baseline — no significant antibody response |
| 1:80 | Borderline — repeat in 7–10 days to check for rising titer |
| 1:160 | Clinically significant in endemic areas — active infection likely |
| 1:320 or above | Strongly suggestive of active typhoid infection |
| Rising titer (4-fold increase) | Most reliable confirmation of active infection |
In endemic regions like Kolkata a baseline titer of 1:80 can occur in healthy individuals. This is why a single Widal result is interpreted alongside symptoms, fever duration, CBC and Typhidot results rather than in isolation.
Widal vs Typhidot — Which is More Accurate?
Key differences between Widal and Typhidot tests:
- Widal Test — detects antibodies to O and H antigens. Best after Day 7–10 of fever. Less specific in endemic areas as background titers are common. Risk of false positives. Inexpensive and widely available.
- Typhidot Test (IgM/IgG) — detects IgM and IgG antibodies to a specific 50 kDa outer membrane protein of S. Typhi. More sensitive and specific than Widal. IgM appears from Day 4–5. Better for early diagnosis. Less affected by past vaccination.
- Blood Culture — the definitive gold standard for typhoid diagnosis. Identifies the actual bacteria. Most sensitive in the first week of fever. Takes 3–5 days for results.
- Best practice — Order Typhidot for early diagnosis (Days 4–7). Order Widal after Day 7 alongside CBC and Typhidot for confirmation. Blood Culture for definitive diagnosis when available.
Symptoms That Should Prompt Typhoid Testing
Get tested if you experience:
- Prolonged continuous fever above 38.5°C lasting more than 5–7 days
- Headache and extreme weakness
- Abdominal pain, distension or tenderness
- Loss of appetite and nausea
- Constipation in early stage or diarrhea in later stage
- Rose-coloured skin spots on abdomen (rose spots — rare but specific)
- Relative bradycardia (slow pulse despite high fever)
- Recent consumption of street food or contaminated water
What Conditions Does the Widal Test Help Diagnose?
- Typhoid fever (S. Typhi)
- Paratyphoid fever Type A (S. Paratyphi A)
- Paratyphoid fever Type B (S. Paratyphi B)
- Differentiation from malaria, dengue and viral fever in undifferentiated fever
Widal Test Price in Kolkata
Widal Test Price: ₹410
No fasting required | Best after Day 7 of fever | Free home collection above ₹2,000
No fasting required | Best after Day 7 of fever | Free home collection above ₹2,000
Tests Commonly Ordered Alongside Widal
- Typhidot (IgM/IgG) — more sensitive early test ordered alongside Widal for comprehensive typhoid diagnosis
- CBC (Complete Blood Count) — typhoid typically causes leukopenia (low WBC), eosinopenia and relative lymphocytosis. Platelet count is also monitored.
- Dengue NS1 + IgM/IgG — dengue and typhoid share symptoms and both are common in Kolkata
- Malaria Antigen + MP Smear — malaria must be ruled out in any undifferentiated prolonged fever
- Blood Culture — definitive diagnosis when Widal is equivocal
- LFT (Liver Function Test) — typhoid can cause hepatitis with elevated SGPT and SGOT
Home Collection for Widal Test in Kolkata
Apollo Diagnostics provides priority home blood sample collection for Widal tests across North and Central Kolkata. Since typhoid patients are extremely weak and should not travel, home collection is strongly recommended. Our phlebotomists arrive at your doorstep with sterile equipment and samples are processed at our NABL-certified central laboratory.
- Home collection available: 7:00 AM – 2:30 PM Daily
- No fasting required — test any time of day
- Priority collection for febrile patients
- Free home collection on orders above ₹2,000
- Digital reports delivered to WhatsApp within 10–12 hours
Quick Links
→ Apollo Diagnostics Nagerbazar → Full List of Individual Tests → Book Home Collection → Full Body Checkup Packages
→ Apollo Diagnostics Nagerbazar → Full List of Individual Tests → Book Home Collection → Full Body Checkup Packages
Frequently Asked Questions
Q1. What is the Widal test used for?
The Widal test detects antibodies to Salmonella typhi and Salmonella paratyphi bacteria in the blood to diagnose typhoid and paratyphoid fever. It is most reliable after the first week of continuous fever when antibody levels have risen to detectable levels. It helps differentiate typhoid from other causes of prolonged fever like malaria and dengue.
Q2. What is a significant Widal titer?
A titer of 1:160 or higher for S. Typhi O or H is generally considered clinically significant for active infection in endemic areas like Kolkata. However a single titer reading can be misleading in endemic populations where background titers are common. A 4-fold rise in titer between two samples taken 7–14 days apart is the most reliable confirmation of active typhoid infection.
Q3. Does the Widal test require fasting?
No. The Widal test does not require fasting. The blood sample can be taken at any time of day. The test is most accurate after the first 7–10 days of continuous fever when antibody levels are measurable. A negative Widal in the first 5 days does not rule out typhoid.
Q4. What is the Widal test price at Apollo Diagnostics Kolkata?
The Widal test price at Apollo Diagnostics is ₹410. No fasting required. Home collection is available free on orders above ₹2,000.
Q5. What is the difference between O and H antibodies in Widal?
S. Typhi O antibodies target the somatic (body) antigen of the bacteria and appear early in active infection — they are more specific for current active disease. S. Typhi H antibodies target the flagellar antigen and appear later. High H titers can indicate a later stage of infection, past infection or typhoid vaccination. High O titer with high H titer together is most suggestive of active current infection.
Q6. Why is Widal not considered fully reliable in Kolkata?
Kolkata is a typhoid-endemic area where a large proportion of the healthy population has background Widal titers of 1:80 due to prior subclinical exposure. This makes a single Widal result of 1:80 or even 1:160 difficult to interpret in isolation. False positives can also occur in malaria, dengue and other febrile illnesses. This is why Widal should always be interpreted alongside clinical symptoms, CBC, fever duration and ideally a Typhidot test or blood culture for confirmation.
Q7. What is the difference between Widal test and Typhidot test?
The Widal test detects agglutinating antibodies to O and H antigens and is best after Day 7. The Typhidot test (IgM/IgG) is more specific — it detects antibodies to a specific outer membrane protein of S. Typhi. Typhidot IgM can be positive from Day 4–5 and is more sensitive for early diagnosis. Typhidot is less affected by background titers and prior vaccination. Both tests complement each other when ordered together.
Q8. Is home collection available for Widal test in Kolkata?
Yes. Apollo Diagnostics provides priority home blood collection for Widal tests across Dum Dum, South Dum Dum, Nagerbazar, Satgachi, Baguiati, Lake Town, Bangur, Kaikhali, Sealdah, Entally, Phoolbagan, Tangra and surrounding areas. Typhoid patients should not travel — book home collection by calling or WhatsApping +91 8660434628.
Q9. How long does it take to get Widal test results?
Widal test results are typically delivered within 10–12 hours of sample collection. Reports are sent digitally to your WhatsApp or email for immediate sharing with your doctor.
Q10. Which centre processes my Widal sample in Kolkata?
All samples collected across North and Central Kolkata are processed at Apollo Diagnostics Nagerbazar — Nandarani Apartment, 8A Narasingha Avenue, Nagerbazar, Dum Dum, Kolkata 700074. Our lab is NABL-certified and ISO-certified.
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