Stool parasites – laboratory test

Description

Why test stool for parasites?

Microscopic examination of stool detects eggs, cysts, larvae and adult forms of intestinal parasites: Giardia, human roundworms, tapeworms, whipworms and, following travel, amoebae and other protozoa. Parasites are shed intermittently, so a single sample has limited sensitivity and the standard is three samples taken at 2–3-day intervals. Threadworms require a separate test (perianal swab), as their eggs are usually absent from stool.

When to consider this test

• chronic or recurrent diarrhoea, abdominal pain, bloating, nausea, weight loss, loss of appetite,
• in children: teeth grinding, restless sleep, recurrent abdominal pain, anaemia (if there is anal itching: a swab for threadworms),
• raised eosinophils on a full blood count, unexplained iron or B12 deficiency,
• after returning from tropical countries, swimming in lakes or eating raw meat or fish,
• household members of someone with a diagnosed infection, people working with children or in catering (sanitary and epidemiological screening),
• checking treatment effectiveness (usually 2–4 weeks after treatment).

How to collect the sample

• Buy a sterile container with a scoop from a pharmacy or collection point. Pass stool into a clean, dry receptacle or onto a toilet collection device; it must not mix with urine or water.
• Use the scoop to take portions from three different areas of the stool, especially those containing mucus or blood, filling approximately 1/3 of the container (a walnut-sized amount).
• Label the container with your first name, surname, date and time. Deliver it as soon as possible; if necessary, refrigerate for up to 24 hours.
• If you see a worm fragment, place it in a separate container with a little water or saline.
• Wait 7–10 days after bismuth or barium preparations (X-ray contrast, RTG), and 2–3 weeks after antibiotics and antiparasitic medicines. Antidiarrhoeal medicines, antacids and mineral oils interfere with the result.

How to interpret the result

Other tests to consider

For anal itching: a swab for threadworms; for diarrhoea: Giardia lamblia antigen in stool, calprotectin, stool culture; for a general assessment, a full blood count (eosinophils) and ferritin. Read more: Badania-Medyczne.pl.

Sources: ALAB laboratoria, Stool parasite testing (collection from 3 areas, 3 samples over 10 days, storage, medicines that interfere with testing); CDC DPDx, Stool specimen collection (three samples at 2–3-day intervals, waiting 7–10 days after barium and bismuth, 2–3 weeks after antibiotics). This information does not replace a medical consultation.