A comparative study of widal test with blood culture in the diagnosis of typhoid fever in

febrile patients Pembimbing :

dr. Rahmi Dewi Sp.PD

ASTRID AVIDITAH2A010007

A comparative study of widal test with blood culture in the diagnosis of typhoid fever in febrile patients

• Gizachew Andualem, Tamrat Abebe, Nigatu Kebede, Solomon Gebre-Selassie, Adane Mihret and Haile Alemayehu

• BMC Research Notes 2014, 7:653• http://www.biomedcentral.com/1756-0500/7/653

BackgroundTyphoid fever

is a systemic prolonged febrile illness caused by certain Salmonella serotypes including Salmonella typhi, S. paratyphi A , S. paratyphi B and S. paratyphiC. – Human being is the only reservoir host– Transmitted fecal-oral

• more likely to be seen in India, South and Central America, and Africa

• areas with rapid population growth, increased urbanization, and limited safe water, infrastructure, and health systems

• Diagnosis of typhoid fever– clinical signs and symptoms– serological markers– bacterial culture– antigen detection and DNA amplification – Blood, bone marrow, stool culture most reliable diagnostic

expensive, often unavailable– Widal test most widely used.

relatively cheaper, easy to perform and requires minimal training and equipment

• Widal test– the value of the test to diagnose typhoid fever has

been debated for as many years as it has been available

– It relies classically on the demonstration of a risingtiter of antibodies in paired samples 10 to 14 days apart

– such a rise is not always demonstrable, even in blood culture-confirmed cases

Interpreting the test has been such a problem that different cut offs have been reported fromn different places

patient management cannot wait for results obtained with a convalescent-phase sample a treatment decision must be made on the basis of the results obtained with a singleacute-phase sample

evaluating the result of a single Widal test is necessary for correct interpretation

This study was carried out to evaluate the value of a single acute-phase Widal test result by blood culture for thediagnosis of typhoid fever in febrile patients in St. Paul’sGeneral Specialized Hospital, Addis Ababa , Ethiopia.

Methods

• Area & periodSt. Paul’s general Specialized Hospitals, Addis Ababa, Ethiopia from December 2010 to March 2011

• Study design prospective study

• Population 277 suspected febrile patients

Blood culture

Blood sampling

Inoculation in culture medium

Biochemical screening Incubated again for 7 days, subculture before reported (-)

Widal test

Qualitative slide agglutination Semiquantitative tube agglutination (titration)

1 drop of S. O & H antigen + 1 drop serum

Rotated 100 rpm 1 min

reactive Non reactive

Serially dilute serum sample with 0,95% saline from 1/20-

1/640

+ 1 drop of S. O & H antigen

O 1/80 & > H 1/160 & >

Recent infection of typhoid

Weakly reactive

Titration test

Result

• Quantitative slide agglutination test

• Semi quantitative (titration)

• Blood culture

High antibody titer in non typhoidal infection

Conclusions

• Sensitivity 71,4 %widal test detects 71,4% of patients with typhoid fever (true positives) but 28,6% with the typhoid fever go undetected (false negatives).

• Specificity 68,44%correctly reports 68,44% of patients without TF as test negative (true negatives) but 31,6% patients without TF are incorrectly identified as test positive (false positives).

• Positive predictive value (PPV) 5,7%possibility for having typhoid fever when widal test result (+) 5,7%

• Negative predictive value (NPV) 98,9%possibility for not having typhoid fever when widal test result (-) 98,9%

• A high antibody titer development is also seen in nontyphoidal febrile infections

Using Widal test as the only laboratory test for the diagnosis of typhoid fever will result in misleading diagnosis

THANK YOU