Transcript Welcome to Journal club - Mymensingh Medical College

Welcome to Journal club
Dr. Md. Abul Hossain Khan
Honorary Trainee
Department of microbiology, MMC
A Comparative Study of Typhidot and
Test in Patients of Typhoid Fever
Widal
Introduction 1
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Typhoid fever is a life threatening systemic infection
occurring in developing areas of the world and a
major public health problem.
Annually at least 16 million new cases of typhoid
globally and more than 13 million cases in Asia and
causing more than six lakhs deaths worldwide.
Blood culture and widal test are routinely employed
investigations for diagnosis of typhoid fever in all
clinical settings.
Introduction 2
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Widal test has been used in the diagnosis of
typhoid illness for long time in our country but it
remains a serological test with a moderate
sensitivity and specificity.
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Therefore, a reliable and easy to perform
serodiagnostic test with a higher sensitivity and
specificity than widal test is required for rapid
diagnosis and management of typhoid cases &
reducing morbidity and its complications.
Introduction 3
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Typhidot is a rapid serological test for the diagnosis
of typhoid fever.
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However, its specificity and sensitivity as compared
to widal test has not been studied so far in our
region.
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Few studies conducted in India and other parts of
Asia have reported encouraging results.
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In view of this, the present study was conducted to
know its utility and effectiveness in diagnostic
yields as compared to widal test in this region.
Materials and Methods
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Typhidot test is a dot ELISA kit.
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The test is based on the presence of specific IgM
and IgG antibodies to a specific 50KD OMP
antigen of the Salmonella typhi.
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The typhidot test becomes positive within 2-3 days
of infection and separately identifies IgM and IgG
antibodies.
Interpretation of Typhidot
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A positive IgM was interpreted clinically as acute
typhoidal illness
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While IgM and IgG positive were taken as acute
typhoidal illness in middle stage of infection
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IgG positive was interpreted as chronic carrier or
previous infection or reinfection.
Result
In this study, 80 acute febrile illness patients were
included and divided into 2 groups:
- Group I: 56 patients with clinical diagnosis of
typhoid fever and
- Group II: 24 patients of suspected Non-typhoidal
fever.
 Routine investigations(CBC, urine analysis and
culture, CXR, LFTs), blood culture, widal test and
tyhidot test were done in all patients.
 Results of blood culture, widal, and typhidot test
were compared in all patients for their sensitivity
and specificity.
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Observations
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In group I: Blood culture was positive in 38,
widal test was significance in 32 & typhidot
tests were positive 44 out of 56 patients
In group II: All were(24 patients) blood
culture negative & 4 patients (17 %) were
widal significance , while only 3 (12 .5 %)
tests were positive for typhidot.
Comparison of Blood culture, widal test
and Typhidot
Test
Typhoid Cases
(n = 56) Group I
Non-typhoidal case
(n=24) Group II
Blood culture
38(68%)
0
widal test
32(57%)
4(17%)
Typhidot
44(79%)
3(12.5%)
Comparison of Widal test and Typhidot tests
in Culture Proven Cases and Non-Typhoid Cases.
Test
Culture Positive
Typhoid Cases
(n = 38 )
Non-Typhoid
Case
(n=24)
Widal
24(74%)
4(17%)
Typhidot
35(92%)
3(12.5%)
On comparative evaluation of widal
test, typhidot and blood culture:
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Widal test: Sensitivity- 57% and specificity - 83%,
Blood culture: Sensitivity- 68% and specificity-100%
Typhidot test: Sensitivity-79 % and specificity-87.5%
Amongst all the 38 patients in Group I, who were
having positive blood culture, typhidot test was
positive in 35 patients, giving a sensitivity of 92%, a
specificity of 87.5% and a positive predictive value of
92% as compared to widal test which was positive in
28 patients with a sensitivity, specificity, positive
predictive value of 74%, 83%, and 87.5%
respectively.
Discussion
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Typhoid fever is a systemic illness with a
significant morbidity and mortality in
developing countries.
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Poor sanitation, overcrowding, low standard
of
living,
lack
of
medical
facilities,indiscriminate use of antibiotics and
lack of vaccination lead to endemicity of
typhoid fever and multi-resistant strains of
Salmonella typhi in developing countries.
Discussion
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Blood culture has remained the gold standard test
in diagnosis of typhoid fever, but its utility in early
diagnosis is limited in early phase of illness
thereby making the isolation of the organism
difficult.
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Widal test has been used for over a century in
developing countries for diagnosing typhoid fever
but it has a low sensitivity, specificity and positive
predictive value, which changes with the
geographical areas.
Discussion
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Similar study carried out in the southern part of
India reported typhidot of having a sensitivity of
100% and a specificity of 80%
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In another study group of typhoid patients in
Pakistan, typhidot test had a comparable
sensitivity of 94% and specificity of 77%, while
widal test had a sensitivity and specificity of 63%
and 83% only.
Discussion
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The effectiveness of typhidot test was also studied in
two different studies in Malaysia. Its sensitivity and
specificity was reported as 90.3% and 91.9%
respectively in the first study and
In second study, also showed a sensitivity and
specificity of 98% and 76.6% respectively.
Both the Malaysian studies showed it to be a better
test in contrast to widal test for rapid diagnosis.
Conclusions
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Typhidot test is a highly sensitive and specific
test in diagnosing typhoid fever.
It is a rapid, easy to perform, more reliable test
for typhoid fever as compared to widal test and
can be useful in early institution of therapy.
However, a larger prospective study would be
required to fully evaluate the usefulness of this
test in countries endemic to typhoid fever.