Typhoid fever & Widal Test

 

My widal test is 1:80 . Am I having Typhoid ?
This is the common question I get in my practice .

Any lab test MUST be interpreted in the context of the symptoms of the patient and in the local pattern of infections prevalent at that time . Just because  a person is having widal positive( >1:80)  , does NOT mean its typhoid .

In flu/viral fever  season or corona wave , a person is more likely to suffer fever from flu/viral fever  or corona rather than typhoid . If the patient seems to be having seasonal viral fever( fever, body pains, cough, cold , throat pain etc )  , there is no point in ordering widal test in the first place . But if the person is having fever suggesting typhoid ( fever, nausea, abdominal pain, headache, constipation  etc ) then there is some logic in doing  tests to detect typhoid like blood culture but not widal .
I have seen patients having  confirmed Corona or Dengue infection , being treated for Typhoid just because  widal was positive . Valuable time was lost as the widal test mislead the doctors initially and the patient received wrong treatment with fatal outcome .

Even if it is done routinely , single value of widal  is NOT reliable (even 1: 320). If there is a four-fold rise in the titer in two samples taken at an interval of minimum 7–10 days, then it can point to typhoid but it needs to be confirmed by blood culture . Eg 3rd day of fever it shows 1:80 , 10 th day of fever is 1: 320  (in the same lab by the same method ) , then it can be considered as  some evidence of typhoid but even then its not confirmatory.

In regular practice ,most of the doctors do not order it a second time( due to cost, inconvenience & pain of taking blood again esp from kids  )  .So the patient is left with a false label of Typhoid based on a single value .Patients panic & want to get admitted or take injections immediately with single value of 1:80 which is completely unnecessary & puts additional stress &  financial burden on the patients & families .

Widal is completely unreliable to diagnose typhoid .In developing countries where the infection is very common ( India , Bangladesh , Pakistan etc) ,even a perfectly normal person without any fever , residing in these regions will show some positivity to widal ( False positive) .  False positive widal is also seen in patients with other infections( bacteremia ,malaria, typhus, cirrhosis etc)  & also prior typhoid vaccine alters it.

In cases with real typhoid fever ,widal test shows negative in 30% of cases.( False negative )
The World Health Organization( WHO)  does NOT recommend  widal test for diagnosing typhoid . The standard text books for doctors do NOT recommend widal to diagnose typhoid . Even guidelines issued by Indian Academy of Pediatrics( IAP) do NOT recommend the use of widal to diagnose typhoid .It is not being done in developed countries like USA  .

A positive blood culture test is completely reliable & is the best test for confirming typhoid. A negative culture, however, does not rule out typhoid fever.Most  patients are given  antibiotics unnecessarily before any blood culture is done  & this  reduces the chance of detecting the bacteria & confirming typhoid. Ideally when typhoid is suspected its important to do a blood culture first & then start antibiotics.

Bottom line :Avoid doing Widal test to diagnose Typhoid  . Do NOT label it as Typhoid just because its Widal positive.

References
1) Harrisons Principles of Internal Medicine 20th ed
2) Nelsons Textbook of Pediatrics 21st ed
3) World Health Organization
4) https://iapindia.org/pdf/Ch-032-Typhoid-IAP-Parental-Guideline-13122021.pdf