Widal test and blood cultures
- evacafe
- sgdeodhare
- thanjones
- sanju4uif
- mahabub01
- BRIDGET2
- aejohani
- NealC
- dr_raj
- NealC
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» evacafe - some questions about widal test
Dear sir,As i live in HK and the widal tests are very common test to be ordered. As i know there will have some false positive under the test. And i want to know as if only the "O" antigen show the low (1/50 or 1/100)titre, and the other show negative, is it significant for diagnosis. As i am a lab technician, how can i report the result?
Can the result of widal test result only used for diagnosis of typhoid fever???
And if the 'O'antigen show in high titre(1/200 or 1/400), but the stool and blood show negative, can it be indicated have the chance to be in acute infection of typhoid fever??
Why we usually note the positive reaction in the 'O' antigen only?? And the blood and stool culture show negative as when the Widal test show positive, is it may due to the treatment started before the test request? Can you give me some hint about ...why the above reaction showed when in acute infection??
Thank you for your attention.
Ching Yee
-- posted by evacafe
-- posted by sgdeodhare
» thanjones - Re: Re: some questions about widal test
Can the result of widal test result only used for diagnosis of typhoid fever???And if the 'O'antigen show in high titre(1/200 or 1/400), but the stool and blood show negative, can it be indicated have the chance to be in acute infection of typhoid fever??
Why we usually note the positive reaction in the 'O' antigen only?? And the blood and stool culture show negative as when the Widal test show positive, is it may due to the treatment started before the test request? Can you give me some hint about ...why the above reaction showed when in acute infection??
Thank you.
thanjones
-- posted by thanjones
-- posted by mahabub01
» BRIDGET2 - widal test
Re: some questions about widal testCan the result of widal test result only used for diagnosis of typhoid fever???
And if the 'O'antigen show in high titre(1/200 or 1/400), but the stool and blood show negative, can it be indicated have the chance to be in acute infection of typhoid fever??
Why we usually note the positive reaction in the 'O' antigen only?? And the blood and stool culture show negative as when the Widal test show positive, is it may due to the treatment started before the test request? Can you give me some hint about ...why the above reaction showed when in acute infection??
Thank you.
-- posted by BRIDGET2
-- posted by aejohani
» NealC - Re: widal test
In response to message posted by BRIDGET2:"Can the result of widal test result only used for diagnosis of typhoid fever???"
No,people with other salmonella infections and with Brucellosis can have a positive widal test.
If a person has been immunized against typhoid fever they can have a positive test and other
gram negative rods in the colon can cause a widal test to be positive. There are also a large
of false negative widal tests (they have typhoid fever but the test is still negative).
"And if the 'O'antigen show in high titre(1/200 or 1/400), but the stool and blood
show negative, can it be indicated have the chance to be in acute infection of typhoid fever??"
Culture of the organism is the best test. However, if someone has been treated with
antibiotics around 50 percent of those with this disease will not result in growth of the
bacterium from stool or blood.
"Why we usually note the positive reaction in the 'O' antigen only??"
The "O" antigen demonstrates the person has an acute infection. This is especially the case when
two different blood samples are taken. If both are positive for the widal test and the second
blood sample has at least a four fold increase in titer then it is likely that the person has
an acute case of typhoid fever. The 'H' antigen is used only for typing the particular salmonella
strain that maybe infecting the patient.
"And the blood and stool culture show negative as when the Widal test show positive, is it may due to the treatment
started before the test request? Can you give me some hint about ...why the above reaction
showed when in acute infection??"
Frequently people that have been given an antibiotic will not have any salmonella in the blood or stool. That is because the antibiotic has killed most of the salmonella and the numbers of salmonella in the blood and stool are too low to be detected by culture. The widal
looks at antibodies already produced by the body to the infection. Antibiotic therapy would not
get rid of the antibodies. It might lower the amount of antibodies produced because the infectious process was slowed down or eliminated by the antibiotics. But antibiotics would not eliminate the antibodies formed to salmonella that are already in the bloodstream. Hope that helps.
Here are some webpages that might help.
http://www.gpnotebook.co.uk/simplepage.c...
http://www.rcpa.edu.au/pathman/typhoid_....
-- posted by NealC
» dr_raj - Re: Re: Re: Widal test and blood cultures
In response to message posted by supergiaf:sir i think widal efficacy is less important than blood culture now a days so we only start prophylactic medication either any of sensitive or any drug antibiotic responding in 12 hours so widal is prophlactic investigation sir please reply any reply will be wellcome
bye
-- posted by dr_raj
» NealC - Re: Re: Re: Re: Widal test and blood cultures
In response to message posted by dr_raj:You are correct the widal test is less sensitive than blood culture so most look for Salmonella in the blood. In some countries with less resources the widal test is still used for diagnosing typhoid fever because it is less expensive than doing cultures or because the clinic the tests are being performed in do not have the ability to culture for the organisms in the blood.
I don't know for sure if the widal test is used to see if antibiotic therapy has been effective. That I will have to look up.
-- posted by NealC
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