Want to know why almost every laboratory test comes back positive for typhoid fever when you have malaria?
For years, we have all joked about how almost every time you walk in the lab to get a malaria test done, it always comes back positive. What is more? It is also always positive for typhoid fever.
But the question is, do you or your loved one really have typhoid or malaria?
Many African countries, Nigeria inclusive, are endemic for malaria parasite; meaning there’s always some level of disease present. As a result, many persons may be infected or they may still carry antibodies for a recent infection. Typhoid is slightly different. Unlike malaria, it is caused by the Salmonella bacterial infection when infected foods/fluid is consumed.
So what are the chances that the lab tests are 100% correct of the time?
Well, that chance is way less than 100%. The widal test is commonly used to test for typhoid and if the person already has malaria, cross reaction between the malaria parasite and typhoid antigens will very likely give a false positive widal test
Other reasons that give a false positive widal test include:
- Previous typhoid immunization
- Recent use of antibiotics
- Laboratory errors (not knowing the endemic baseline titer)
- Previous non-typhoid Salmonella infection
- Other diseases like typhus, cryptococcal meningitis, immunological conditions and chronic liver disease.
The widal/typhoid test is not diagnostic until at least two tests are done and compared. A positive widal test does not necessarily mean typhoid disease. This is one reason why history, clinical symptoms/signs, examinations and other investigations are very important when treating diseases.
Next time you feel ill and you get positive widal tests, ask your doctor if the widal test can be repeated. Unless of course he or she advises otherwise.
Credit: Dr. Kharis