Explanation

Entamoeba histolytica (feces): what is measured?

Entamoeba histolytica is a single-celled parasite that can invade the wall of the large intestine. Infection spreads through stool, usually through contaminated water or food in countries with poorer hygiene. Under the microscope, this parasite cannot be distinguished from the harmless Entamoeba dispar; that requires a PCR or a specific antigen test. So the method the laboratory uses determines how the result should be read.

What can it detect?

Amebiasis: an intestinal infection that ranges from no symptoms to bloody diarrhea (amebic dysentery)
Rarely: an inflammation with pus in the liver (liver abscess)

Result

What does the result mean?

Positive result

A positive result with a test that specifically detects Entamoeba histolytica fits an infection with this parasite. Many people have no symptoms from it; others get diarrhea, sometimes with blood and mucus, and abdominal pain. Rarely, the parasite spreads to the liver. If the result was obtained with the microscope, it may also be the harmless Entamoeba dispar.

Negative result

A negative result means that the pathogen was not found in this stool sample. Some pathogens are shed irregularly, and shortly after infection the pathogen sometimes cannot be detected yet; so an infection is not always ruled out. According to Thuisarts.nl, diarrhea is usually caused by stomach flu; diarrhea that lasts longer than 2 weeks can also have other causes, such as medicines, not tolerating lactose well or an irritable bowel.

After an abnormal result

In a confirmed infection with Entamoeba histolytica, the doctor usually treats with a medicine against the parasite, even if you have no symptoms, because the parasite can still cause illness later. If the result was obtained with the microscope, a PCR often follows first to distinguish Entamoeba histolytica from Entamoeba dispar. Amebiasis is not notifiable in the Netherlands; the disease is not on the list of the Dutch Public Health Act.

Reliability

How reliable is the test?

Testing the stool for pathogens that cause intestinal infections is routine testing in Dutch laboratories. According to the LCI guidelines (RIVM), a PCR is preferred over microscopy or culture for most pathogens, because it is more sensitive; a culture is sometimes still needed afterwards to type the bacterium or test its sensitivity to antibiotics. According to Thuisarts.nl, stool testing for diarrhea is mainly useful if you are very ill or if the diarrhea lasts longer than 2 weeks and does not get better; short-term diarrhea is usually caused by stomach flu and usually clears up on its own.

What can affect the result?

Parasites and worm eggs are shed irregularly; one sample can miss an infection, which is why laboratories sometimes ask for samples from several days.
Shortly after infection, the pathogen may not yet be detectable in the stool.
The longer the sample is in transit, the smaller the chance of a positive culture.
A PCR can also find genetic material from a pathogen that is no longer alive or from an infection that has already passed.

Preparation

Fill the three tubes on three different days, one tube per day. Parasites are not in the stool every day.
Do not collect stool during your period.

Who it is for

Who is the test useful for?

Useful for

According to Thuisarts.nl, stool testing is useful if you are very ill from diarrhea, or if the diarrhea lasts longer than 2 weeks and does not get better, including after travel. In people without symptoms, a positive result says less, because it may fit carriage or an infection that has already passed. Without symptoms, testing is mainly useful if the GGD (municipal public health service) asks for it, for example during an outbreak or because of work in the food sector or in healthcare.

How common is it?

Diarrhea is common and, according to Thuisarts.nl, is usually caused by stomach flu; bacteria and parasites are less often the cause. According to the LCI guidelines (RIVM), a few hundred to over a thousand infections with, for example, Salmonella, Shigella or Cryptosporidium are confirmed by a laboratory in the Netherlands each year, and the real number is much higher because most people are not tested. After travel to a country with poorer hygiene, the chance of a bacterial or parasitic intestinal infection is higher.

LCI guidelines (RIVM) and Thuisarts.nl

Get tested