Widal test seem to be the commonest laboratory investigative tool for Typhoid fever and the serology titre for significant result seems different from different laboratory setting in endemic region,even possibly in non clinical subject , how can we measure the effectiveness of widal test for Typhoid fever where water supply is still a problem.
Though the negative test may not exclude typhoid, the positive test (titre of >1/160) will be useful in culture negative, or when blood or stool cultures are not practical, or in out-patient settings. In Sri Lanka, the country is considered endemic and often the disease is diagnosed with the suggestive clinical presentation. The disease is more prevalent in urban areas where culture facilities are usually available in tertiary care centers but the prior antibiotics render the cultures negative. I, though not often, still use widal to get a clue in difficult cases. Please read the following research as well;
Trop Geogr Med. 1981 Dec;33(4):329-33, Diagnostic value of the Widal test, Abraham G, Teklu B, Gedebu M, Selassie GH, Azene G.
Clin Diagn Lab Immunol. 2002 Jul; 9(4): 938–941, Widal Test in Diagnosis of Typhoid Fever in Turkey, Ayse Willke,,* Onder Ergonu, and Banu Bayar
I agree that a titre of 1:160 or more for the O antigen by Widal test in single samples is diagnostic of Typhoid fever in developing countries , when other investigations are not available . Typhoid is an important cause of tropical acute febrile illness in developing countries & simple , easy available diagnostic tests are needed to guide primary care doctors . It is preferable to have repeat samples to demonstrate rising titres to confirm diagnosis .
I agree with all of you and thanks for the answers. The cut off titre for particular populationsshould be known. It means widal,a rising titre and culture can confirm clinical diagnosis.Even though we are in a developing country, water ,this precious liquid remains life and stakeholders sholud make sure that no community stays without potable water.
As it was mentioned, the negative widal rest does not exclude typhoid fever. Moreover, the antigens may cross react producing false positive result. Increasing the Salmonella titre in a repeated test few days after is an important tool for diagnosing typhoid fever in endemic areas where the culture is not feasible.
Wahib ,while waiting for follow-up titre ,you may meet the patient in septic shock from perforated typhoid enteritis , the question is simple ,would none clinical subject living in endemic zone not also test positive as well?, more-also cultures are not readily available and results takes time.
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