Stool antigen tests for diarrhoea pathogens

Do you have persistent diarrhoea, blood in stool or illness after travel? Stool antigen tests show whether common intestinal pathogens are responsible: Campylobacter, Shigella, E. coli O157, cholera or astrovirus. This helps a doctor decide on antibiotics and how to prevent infection spreading to household members.

Who the test is for

• people with severe diarrhoea or diarrhoea lasting more than several days, particularly with fever and cramps;
• for bloody or mucus-containing stool;
• after travel to areas with poorer hygiene or suspect food and water, such as undercooked chicken or mince and unpasteurised milk;
• children, older people and those with weakened immunity, who are exhausted more quickly by diarrhoea;
• when several household members or people in a nursery or other group develop diarrhoea;
• people working with food or children when a doctor requests pathogen confirmation.

For dehydration signs (very little urine, dry mouth, unusual sleepiness), severe abdominal pain, much blood in stool or high fever in a young child, seek medical attention immediately or call 194 or 112.

What the test reveals

Each test detects components (antigens) of one pathogen in stool. Tests are separate, so choose those matching your symptoms:

• Campylobacter is among Europe’s most common bacterial diarrhoea causes, most often transmitted by inadequately cooked chicken.
• Shigella causes dysentery: diarrhoea with blood and mucus, fever and cramps. It spreads easily between people.
• E. coli O157 is a toxin-producing strain that can cause bloody diarrhoea. In children and older people it sometimes causes a severe kidney complication (haemolytic uraemic syndrome), making it important for a doctor to know the result before prescribing an antibiotic or antidiarrhoeal.
• Cholera (Vibrio cholerae O1) is exceptionally rare in Croatia. Testing is useful for profuse watery diarrhoea after visiting an area where cholera occurs.
• Astrovirus more often causes milder diarrhoea and vomiting in young children. Antibiotics do not act on viruses.

The procedure and preparation

Collect stool at home in a clean container with a scoop. Preferably sample during the first days of illness and, if possible, before antibiotics. Avoid mixing stool with urine or toilet water. If blood or mucus is present, collect that part. Bring the sample promptly. No special diet is needed beforehand, and handing in the sample takes a few minutes.

What your result means

• Positive: the pathogen’s antigen was found in stool, suggesting it causes the diarrhoea alongside symptoms. Many mild infections resolve with fluids; a doctor decides on antibiotics. Positive cholera tests are always confirmed with additional testing.
• Negative: the antigen was not found. This does not rule out other pathogens such as Salmonella, viruses or parasites; results can also be negative if sampling was late in illness or after antibiotics.

A doctor interprets results alongside symptoms, illness duration and other findings, referring if needed for stool culture or testing stool for cysts and parasites. Some of these infections are notified to the epidemiological service, arranged by a doctor.

How to arrange testing

No referral or appointment is needed: hand in a stool sample at any branch (listed under Contact). Prices for all tests and panels are available in the price list. For suspected viral infection, a more practical option is Viral gastro panel 2, including rotavirus, adenovirus and norovirus alongside astrovirus.

Frequently asked questions

Which test should I choose for bloody diarrhoea?

Shigella, Campylobacter and E. coli O157 are most often investigated in bloody diarrhoea. With blood in stool, speaking to a doctor before testing is best.

Do I need antibiotics if the test is positive?

Not always. Many intestinal infections resolve on their own, and antibiotics are usually not given for E. coli O157. A doctor decides according to pathogen and illness severity.

When can a child return to nursery?

Usually at least 48 hours after the last diarrhoea or vomiting is advised. For some pathogens and food handlers, a doctor or epidemiologist may also request a follow-up result.

What can I do at home during diarrhoea?

Drink enough fluids, preferably pharmacy oral rehydration solution, in small frequent sips. Do not take antidiarrhoeals for bloody stools or fever without medical advice.