Explanation

Parasitology (feces): what is measured?

In parasitology testing, the stool is examined for parasites: single-celled parasites (protozoa), such as Giardia, and worms and their eggs. Depending on the laboratory, this is done with the microscope, a PCR or both. Because parasites are shed irregularly, one sample can miss an infection.

What can it detect?

Intestinal infections caused by single-celled parasites (protozoa), such as Giardia, Cryptosporidium and Entamoeba histolytica
Intestinal worm infections, such as roundworm, whipworm and tapeworm
Single-celled parasites of which it is uncertain whether they cause illness, such as Dientamoeba fragilis and Blastocystis

Result

What does the result mean?

Positive result

A positive result means that a parasite has been found; the result report states which one. Whether it explains the symptoms depends on the species. Giardia, Cryptosporidium and Entamoeba histolytica can cause diarrhea and abdominal pain, and worms sometimes cause abdominal pain, itching around the anus or weight loss. Other single-celled parasites, such as Dientamoeba fragilis and Blastocystis, are also often found in people without symptoms; whether they cause illness is uncertain.

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

The GP assesses for each parasite found whether it explains the symptoms and whether treatment is needed; for most disease-causing parasites and worms, a course of a medicine against parasites or worms is possible. None of the parasites in this test is notifiable for individual cases; only multiple cases of diarrhea in an institution, such as a daycare center or nursing home, must be reported by the institution to the GGD (municipal public health service).

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

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