Today is our topic of discussion Widal test
Widal test
It is the demonstration of salmonella antibodies against the antigens O-somatic and H-flagellar. For salmonella paratyphi only ‘H’ antigen is tested.
Patient’s serum is diluted serially to various dilutions and is made to react antigens O and H. After incubation at the optimum temperature and time, it is examined for agglutination. If agglutination occurs, the test is positive. The limitation of Widal test is that, it is time consuming & it has some fallacy to interpret.
Interpretation of Widal test:
1. A titer of 160 or more for ‘O’ antigen (TO ≥1:160) and/ or 320 or more for ‘H’ antigen ( TH 21:320) is considered significant.
2. Timing of the test: Antibodies begin to arise during the end of first week. The titer gradually increases
up to fourth week after which it declines.
3. Patients treated with antibiotics in the early stages may not give positive results.
4. Patients who have received vaccines against Salmonella may give false positive reactions.)
[Differentiated from true infection by repeat test after a week. True untreated infection show rise of titer]
5. Those who suffered with enteric fever in the past may develop anti-Salmonella antibodies during an unrelated or closely related infection.
[Differentiated from true infection by lack of any rise in titer when repetition after a week]
Indication for referral:
1. Development of complication.
2. Failure to improve after two weeks of continued treatment.
3. Deterioration of the condition
Prognosis:
Pyrexia may persist for up to 5 days after the start of specific therapy. If untreated, fever may persist for three weeks to a month. Death occurs in between 10% and 30% of untreated cases. The chronic carrier should be treated for 4 weeks. Cholecystectomy may be necessary wherein the place of residence of the organism is the gall bladder.
Preventive and control measures of typhoid:
1. Treatment of patients and carriers
2. Health education: Handwashing practice, particularly
3. Sanitary disposal of feces and control of flies.
4. Provision of safe drinking water
5. Immunization for people at special risk (e.g. travelers to endemic areas)
6. Regular check-up of professional cooks.
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