Widal Slide Agglutination Test
About Widal Slide Agglutination Test
| Field | Value |
|---|---|
| Also Known As | Widal Test, Typhoid Test, Widal Agglutination Test, Enteric Fever Test |
| Sample Type | Venous blood (serum) |
| Fasting Required | Not required |
| Report Time | Within 24 hours |
| Recommended For | All genders and ages; primarily adults and children with suspected typhoid symptoms |
| Price | Starting at ₹225 |
What Is a Widal Slide Agglutination Test?
The Widal slide agglutination test is a blood test used to detect antibodies produced by the body in response to a Salmonella Typhi or Salmonella Paratyphi infection. It is commonly ordered when a patient presents with prolonged fever and symptoms suggestive of typhoid or paratyphoid fever, together referred to as enteric fever. A small blood sample is drawn from a vein, and the serum is tested against specific bacterial antigens on a slide. The test is also known as the enteric fever test or typhoid test.
What Does a Widal Slide Agglutination Test Measure?
The Widal agglutination test checks for antibodies against four bacterial antigens. Each antigen corresponds to a different bacterium or a different part of the same bacterium. Here is a brief explanation of each parameter:
| Parameter | What It Detects |
|---|---|
| S. Typhi O (TO) | Antibodies against the somatic (body) antigen of Salmonella Typhi; rise early in active infection and fall soon after recovery |
| S. Typhi H (TH) | Antibodies against the flagellar (tail) antigen of Salmonella Typhi; appear slightly later and may persist after past infection or vaccination |
| S. Paratyphi AH | Antibodies against Salmonella Paratyphi A, which causes paratyphoid fever A |
| S. Paratyphi BH | Antibodies against Salmonella Paratyphi B, which causes paratyphoid fever B |
Why Is a Widal Slide Agglutination Test Done?
A doctor may order this test when typhoid or a related infection is suspected based on symptoms or travel history.
Common Symptoms That May Require This Test
The following symptoms often prompt a doctor to request a Widal test:
- Prolonged high fever lasting more than a few days
- Persistent headache and general fatigue
- Nausea, vomiting, or loss of appetite
- Abdominal pain or discomfort
- Constipation or diarrhoea
- Faint pink spots (rose spots) appearing on the chest or abdomen
- Recent travel to an area where typhoid is common
Conditions This Test Can Help Detect
The Widal agglutination test can help identify the following conditions:
- Typhoid fever, caused by Salmonella Typhi
- Paratyphoid fever A, caused by Salmonella Paratyphi A
- Paratyphoid fever B, caused by Salmonella Paratyphi B
- Enteric fever in general, which covers both typhoid and paratyphoid infections
How to Prepare and What to Expect
Preparation for this test is minimal. Here is everything you need to know before your appointment.
Do You Need to Fast?
No fasting is required for the Widal slide agglutination test. You can eat and drink normally before the sample is collected. If your doctor has ordered additional tests alongside this one, ask whether any of those require fasting.
Practical Tips Before Your Test
A little preparation helps ensure a smooth collection process. Keep the following in mind:
- Drink enough water before your appointment to make blood collection easier
- Inform the phlebotomist (the person drawing your blood) of any medications you are currently taking, especially antibiotics
- Mention any previous typhoid vaccination or past typhoid infection
- Let the phlebotomist know if you have recently travelled to an area where typhoid is prevalent
Step-by-Step Procedure
The collection process is quick and straightforward. Here is what happens from start to finish:
- A trained phlebotomist cleans the skin around a vein, usually at the inside of your elbow, with an antiseptic swab.
- A small blood sample is drawn using a sterile needle and collected into a tube.
- The sample is labelled and sent to the laboratory.
- In the lab, a drop of your serum is placed on each of four labelled circles on a glass slide, alongside the O, H, AH, and BH antigens.
- Each circle is mixed and the slide is gently rocked for up to one minute; visible clumping (agglutination) indicates a positive reaction for that antigen.
- If the screening result is positive, further quantitative testing determines the exact antibody titre (the level of dilution at which agglutination is still seen).
Factors That Can Affect Accuracy
Several factors may influence the reliability of your typhoid test results. These include:
- Testing too early (before the first week of fever) or too late (after the fourth week), when antibody levels may be low
- Prior use of antibiotics, which can suppress antibody production
- Previous typhoid vaccination, which may raise H antigen antibody levels
- Regional baseline antibody levels, which can be higher in areas where typhoid is common
- Conditions such as malaria, chronic liver disease, or immunological disorders that may cause misleading results
Understanding Your Widal Slide Agglutination Test Results
Results should always be reviewed together with your symptoms, medical history, and clinical examination. The table below provides general reference values.
| Parameter | Normal Range | Elevated Titre Interpretation |
|---|---|---|
| S. Typhi O (TO) | 1:80 or below | 1:160 or above suggests active infection |
| S. Typhi H (TH) | 1:80 or below | 1:160 or above may indicate current or past infection, or prior vaccination |
| S. Paratyphi AH | 1:80 or below | 1:160 or above suggests paratyphoid A infection |
| S. Paratyphi BH | 1:80 or below | 1:160 or above suggests paratyphoid B infection |
Please note that titres at or below 1:80 are generally considered within the normal range, though this can vary by laboratory. A four-fold rise in titres between two samples taken 7 to 10 days apart is a strong indicator of an active infection.
These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain medical conditions may cause the enteric fever test to give misleading results:
- Malaria, typhus, chronic liver disease, and cryptococcal meningitis have been associated with false-positive results, meaning the test may appear positive even without a typhoid infection.
- In people living with HIV, false-positive results may occur due to cross-reacting antibodies, while false-negative results may occur because a weakened immune system produces fewer antibodies.
- Recent COVID-19 vaccination may also cause cross-reactivity, leading to an inaccurate reading.
How to Maintain Healthy Levels
These general tips can help reduce the risk of typhoid and related infections:
- Wash your hands thoroughly with soap and water before eating and after using the toilet.
- Drink only safe, treated water and avoid ice made from unknown sources, especially when travelling.
- Eat thoroughly cooked food and avoid raw or undercooked items in areas where typhoid is common.
Lupin Diagnostics Widal Slide Agglutination Test Price and Home Collection
The Widal slide agglutination test is available at an approximate starting price of ₹225, with home sample collection offered across cities in India. The table below shows indicative prices by city.
| City | Approximate Price (₹) |
|---|---|
| Mumbai | ₹330 |
| Bengaluru | ₹260 |
| Hyderabad | ₹250 |
| Chennai | ₹390 |
| Kolkata | ₹225 |
| Pune | ₹330 |
Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
Booking your Widal test is simple and takes just a few minutes:
- Select the test on the Lupin Diagnostics website.
- Choose your city and preferred time slot.
- Opt for home sample collection by a certified phlebotomist, or visit your nearest Lupin Diagnostics centre.
- Receive your report via email or WhatsApp within the stipulated turnaround time.
Home Collection
Lupin Diagnostics offers home collection for the Widal agglutination test across cities in India, so you do not need to visit a centre. All samples are processed in NABL-accredited laboratories, ensuring consistent quality. Your digital report is delivered directly to your email or WhatsApp once ready.
Frequently Asked Questions
The Widal test is used to detect antibodies in the blood that develop in response to a Salmonella Typhi or Salmonella Paratyphi infection. It helps a doctor determine whether a patient's symptoms, such as prolonged fever and abdominal discomfort, are caused by typhoid or paratyphoid fever. The slide method is widely used for rapid screening.
Antibodies against the Salmonella antigens generally appear in the blood after 6 to 8 days of infection. Taking the test before the first week of fever may produce a falsely negative result. For the most meaningful reading, your doctor will typically advise waiting at least one week after fever onset.
No fasting is required before a Widal slide agglutination test. You can eat and drink normally on the day of the test. Do inform your doctor about any medications you are taking, as some medicines may affect your results.
A single test result may not be enough to confirm typhoid, particularly in regions like India where exposure to typhoid-causing bacteria is common. A four-fold rise in antibody titres between two samples taken 7 to 10 days apart gives a much clearer picture. Your doctor will consider the result alongside your symptoms and clinical examination.
Several conditions can cause an elevated result even without a current typhoid infection. These include previous typhoid vaccination, a past typhoid episode, malaria, chronic liver disease, other Salmonella infections, and certain immunological disorders. This is why your doctor will interpret results in context rather than in isolation.
The slide method is a rapid screening test that gives results within minutes. The tube method takes longer (usually overnight incubation) but is considered more sensitive and accurate. The Widal slide agglutination test is widely used for quick, initial screening, particularly in busy clinical settings.
Blood culture is considered the reference standard for typhoid diagnosis, with accuracy of around 70 to 75 per cent during the first week of illness. It can identify the actual bacteria, whereas the Widal test only detects antibodies. However, in settings where blood culture facilities are not readily available, the Widal test remains a practical and useful screening tool.
Widal Slide Agglutination Test
