Widal test

Widal test

The Widal test is a presumptive serological test for Enteric fever or Undulant fever. In case of "Salmonella" infections, it is a demonstration of agglutinating antibodies against antigens O-somatic and H-flagellar in the blood. For brucellosis, only O-somatic antigen is used. It's not a very accurate method, since patients are often exposed to other bacteria (e.g. "Salmonella enteritidis", "Salmonella typhimurium") in this species that induce cross-reactivity; many people have antibodies against these enteric pathogens, which also react with the antigens in the Widal test, causing a false-positive result. Test results need to be interpreted carefully in the light of past history of enteric fever, typhoid vaccination, general level of antibodies in the populations in endemic areas of the world. Typhidot is the other test used to ascertain the diagnosis of typhoid fever. As with all serological tests, the rise in antibody levels needed to make the diagnosis takes 7-14 days, which limits their use. Other means of diagnosing Salmonella typhi (and paratyphi) include cultures of blood, urine and feces. The organism also produces H2S from thiosulfate.

Often 2-mercaptoethanol is added. This agent more easily denatures the IgM class of antibodies, so if a decrease in the titer is seen after using this agent, it means that it's IgM that's high but not IgG. This differentation of antibody classes is important; as it allows for the distinction of a recent (IgM) from an old infection (Ig E)

So we can define this test as " a test involving agglutination of typhoid bacilli when they are mixed with serum containing typhoid antibodies from an individual having typhoid fever; used to detect the presence of Salmonella typhi and S. paratyphi."

ee also

Georges-Fernand Widalwidal test if TO antigen more than 1.160 in active infectionwidal test if TH antigen more than 1.160 in past infection or in immunized

References

* Olopoenia LA, King AL. [http://pmj.bmjjournals.com/cgi/content/full/76/892/80 Widal agglutination test - 100 years later: still plagued by controversy] . "Postgrad Med J" 2000; 76(892): 80-4. PMID 10644383

wida test interpation


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  • Widal test — also Widal s test n a test for detecting typhoid fever and other salmonella infections using the Widal reaction compare AGGLUTINATION TEST * * * Widal serum test (for typhoid and paratyphoid fevers) a test of serum of patients with suspected… …   Medical dictionary

  • Widal test — Widal s test Wi*dal s test, or Widal test Wi*dal test or Widal reaction Wi*dal reaction . [After Fernand Widal (b. 1862), French physician.] (Med.) A test for typhoid fever based on the fact that blood serum of one affected, in a bouillon culture …   The Collaborative International Dictionary of English

  • Widal test — noun a test for detecting typhoid fever and other salmonella infections • Syn: ↑Widal s test • Hypernyms: ↑agglutination test * * * noun see widal s test …   Useful english dictionary

  • Widal test — (ve dahl ) A test involving agglutination of typhoid bacilli when they are mixed with serum containing typhoid antibodies from an individual having typhoid fever; used to detect the presence of Salmonella typhi and S. paratyphi …   Dictionary of microbiology

  • Widal test — noun The agglutination test for typhoid fever …   Wiktionary

  • Widal's test — Wi*dal s test, or Widal test Wi*dal test or Widal reaction Wi*dal reaction . [After Fernand Widal (b. 1862), French physician.] (Med.) A test for typhoid fever based on the fact that blood serum of one affected, in a bouillon culture of typhoid… …   The Collaborative International Dictionary of English

  • Widal reaction — Widal s test Wi*dal s test, or Widal test Wi*dal test or Widal reaction Wi*dal reaction . [After Fernand Widal (b. 1862), French physician.] (Med.) A test for typhoid fever based on the fact that blood serum of one affected, in a bouillon culture …   The Collaborative International Dictionary of English

  • Widal's test — noun a test for detecting typhoid fever and other salmonella infections • Syn: ↑Widal test • Hypernyms: ↑agglutination test * * * noun or widal test Usage: usually capitalized W Ety …   Useful english dictionary

  • Widal reaction — Wi·dal reaction also Wi·dal s reaction vē däl(z) n a specific reaction consisting in agglutination of typhoid bacilli or other salmonellas when mixed with serum from a patient having typhoid fever or other salmonella infection and constituting a… …   Medical dictionary

  • Widal syndrome test (reaction serum test) — Wi·dal syndrome, test (reaction, serum test) (ve dahlґ) [Georges Fernand Isidore Widal, French physician, 1862–1929] see hemolytic anemia, under anemia, and see under test …   Medical dictionary

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