How is food poisoning diagnosed?

How is food poisoning diagnosed?

A medical doctor will most often be able to diagnose food poisoning based on the symptoms present and following a physical examination. If severe, tests may be recommended so as to determine the nature of the pathogen causing the infection, either viral, bacterial or parasitic.

To begin with, a doctor will obtain a detailed medical and or / family history, as well as discuss symptoms in as much detail as possible. He or she may ask questions like:

  • How long ago did symptoms begin?
  • Have symptoms been experienced consistently, or have they ‘come and gone’?
  • Has anyone else known to you developed similar symptoms recently? If so, have these developed shortly after consuming the same foods or meals?
  • What have you eaten recently (particularly in the past few days)?
  • Have you recently been travelling? If so, where? (E.g. camping near a body of potentially contaminated water).
  • Have you noted any blood in either vomit or stools?
  • Have you been feverish?
  • Have any antibiotics been prescribed (and taken) recently (before symptoms began)?

A doctor will conduct a thorough check to assess one’s overall physical condition, and specifically to evaluate any potential signs of dehydration (dry mouth, sunken eyes etc.) and abdominal pain or tenderness. A doctor will check a person’s blood pressure level, temperature and pulse rate as well.

Diagnostic test recommendations will take into account the nature of symptoms (i.e. severity), an overall health history, as well as the types of foods consumed recently. In mild to moderate instances of viral and most bacterial infections, tests are not normally all that necessary for food poisoning. Symptoms are more likely to resolve before test results have been returned.

A doctor may wish to determine the type of pathogen causing illness in more severe instances where symptoms indicate possible complications. To do so, the following may be recommended:

  • Blood test: This may be recommended so as to assess electrolyte levels, as well as check kidney function. If symptoms are severe or there are signs of possible complications, such as haemolytic uremic syndrome, a complete blood count may be performed (checking red blood cells, white blood cells and platelet counts). Liver function may also be checked if there are suspicions of a hepatitis infection. Blood tests are also used to rule out any medical suspicions or underlying conditions.
  • Stool (faeces) culture: A stool sample will be requested for laboratory analysis so as to try and identify the type of infectious organism, or sometimes merely to determine the presence of blood. If infection from salmonella, campylobacter or shigella are suspected (possibly due to the presence of blood in stools) a sample will also be thoroughly analysed for these organisms. Stool samples are also useful for identifying specific parasites (or toxins) causing poisoning, although some are very difficult to identify, even under a microscope.
  • Urinalysis: A urine sample may be requested to assess possible dehydration.
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