Stool Ova and Parasites (Stool Microscopy)

What is a stool parasite examination?

A stool parasite examination is a microscopic search of a stool sample for the eggs, cysts, larvae or motile forms of parasites that can live in the intestines. Giardia, Entamoeba species, Ascaris (known as the intestinal roundworm) and tapeworm species are among the parasites that can be detected with this method. These parasites can be transmitted through contaminated water, poorly washed fruit and vegetables, or settings where hygiene rules are not followed.

During the examination, a small portion of the stool is spread on a glass slide and, when needed, stained with dyes such as Lugol's iodine and examined under magnification. Microscopy can also reveal other findings in the stool, such as white blood cells, red blood cells, fat droplets or yeast cells. These findings give your doctor clues about conditions such as inflammation in the intestine or an absorption problem. The result is reported in descriptive terms based on the structures seen under the microscope.

When is a stool parasite test ordered?

Intestinal parasites sometimes cause no symptoms at all, while at other times they can lead to long-lasting digestive complaints. Your doctor may order this examination when your complaints or living conditions suggest a parasitic infection. Because infection spreads more easily in communal settings such as nurseries and schools, it is a test frequently used in children. The test is also part of the carrier screening carried out for certain occupations.

• Prolonged or recurrent diarrhea, gas and bloating
• Unexplained abdominal pain and loss of appetite
• Poor weight gain or delayed growth in children
• A high eosinophil count on a blood test
• Travel to regions with limited access to clean water
• A parasite found in a family member

How should you prepare for a stool parasite test?

You do not need to fast for this test, and you are not expected to follow a special diet. If you have had a barium X-ray in the past week or two, or have taken a laxative, an antacid or an antidiarrheal medicine, mention this; these substances can make parasites harder to see. A sample given before parasite treatment or antibiotics are started helps you get a more accurate result. If you take medicines regularly, do not stop them without consulting your doctor.

The stool should be passed onto a clean, dry surface without mixing with urine or toilet water, and a hazelnut-sized sample should then be taken using the spoon provided with the container. Because the motile forms of parasites in watery stool can deteriorate quickly, it is important that the stool reaches the laboratory fresh. If you would like to give the sample at home, a sterile container is brought to you, you collect the sample yourself, and the nurse picks it up shortly afterwards. Because parasites may not be passed in the stool every day, your doctor may ask for more than one sample collected on different days.

What does a stool parasite result mean?

The statement "no parasites detected" in the report means that no parasite eggs, cysts or other forms were seen in the sample examined. Because parasites can be shed intermittently, a single negative result does not rule out an infection with certainty. If your complaints persist, your doctor may also order antigen tests, which are more sensitive for parasites such as Giardia. Pinworm eggs, on the other hand, are usually looked for not in the stool but with a separate test, using transparent tape pressed around the anus in the morning.

When a parasite is detected, its type is stated in the report, and your doctor decides whether treatment is needed and, if so, whether family members should also be assessed. Because the disease-causing role of some organisms such as Blastocystis is debated, the result is always interpreted together with your complaints. White or red blood cells in the stool may suggest an inflammatory process in the intestine. The reporting format and reference wording may vary by laboratory; this laboratory's reference is shown on this page. All findings should be evaluated by your doctor together with your symptoms and other tests.