Stool Adenovirus/Rotavirus Test: Uses & Results

What Is the Stool Adenovirus and Rotavirus Antigen Test?

Every winter, I see children and adults with acute diarrhea, vomiting, and fever. In my clinic, the first suspicion often falls on viral gastroenteritis, and the stool Adenovirus/Rotavirus antigen test is a rapid, reliable way to confirm the cause. This test detects specific proteins (antigens) from Rotavirus and Adenovirus serotypes 40/41 in a stool sample. Both viruses are leading causes of infectious diarrhea worldwide, especially in young children.

Why Is This Test Ordered?

My patients typically present with sudden-onset watery diarrhea, nausea, and low-grade fever. The test helps differentiate viral gastroenteritis from bacterial or parasitic infections, guiding appropriate treatment and infection control. It is particularly useful in:

• Infants and young children with severe diarrhea
• Outbreaks in daycare centers, schools, or nursing homes
• Immunocompromised patients who may have prolonged viral shedding
• Travelers returning from regions with high rotavirus prevalence

Reference Ranges (Qualitative Results)

This is a qualitative test — the result is reported as either “Negative” (no viral antigens detected) or “Positive” (viral antigens present). Reference ranges are the same for all age groups and both genders.

What Does a Positive Result Mean?

A positive result indicates active infection with the detected virus. Rotavirus is the most common cause of severe diarrheal illness in children under 5, responsible for about 200,000 emergency visits annually in the US alone. Adenovirus serotypes 40/41 cause similar symptoms but can also be seen year-round. In my practice, I explain that a positive result confirms viral gastroenteritis and that antibiotics are not needed — management focuses on fluid replacement and supportive care.

What Does a Negative Result Mean?

A negative result means no viral antigens were detected, but it does not entirely rule out viral infection. The test may be negative if the sample is taken too early or late in the illness, or if the cause is a different virus (e.g., norovirus, astrovirus). If symptoms persist, additional stool tests (culture, PCR) may be warranted.

How Is the Test Performed?

The test uses a small stool sample (about the size of a walnut) collected in a clean container. The lab applies a rapid immunoassay — similar to a home pregnancy test — that binds viral antigens and produces a color change. Results are usually available within 15–30 minutes. No special preparation (fasting or avoiding medications) is needed.

LOINC Standard Names and Codes

For precision in electronic health records, this test corresponds to two LOINC codes:

• Rotavirus Ag [Presence] in Stool: LOINC 20398-5
• Adenovirus Ag [Presence] in Stool: LOINC 18481-2

Rotavirus Vaccine and Test Results

I am often asked: “Can the rotavirus vaccine cause a positive test?” Live oral rotavirus vaccines (e.g., RotaTeq, Rotarix) can shed virus in stool for up to 2 weeks after vaccination. In recently vaccinated infants, a positive rotavirus antigen test may reflect vaccine strain, not natural infection. Clinical correlation with symptoms is essential. If a vaccinated infant is asymptomatic, a positive result is likely vaccine-related.

Is Rotavirus Dangerous in Adults?

While rotavirus is most severe in young children, adults can contract it (especially if exposed to infected children). In healthy adults, symptoms are usually milder and self-limited. However, elderly or immunocompromised adults can develop dehydration requiring hospitalization. Adenovirus can cause more prolonged illness in immunocompromised hosts.

Adenovirus vs Rotavirus Symptoms

Clinically, both cause watery diarrhea and vomiting, but adenovirus infection often includes respiratory symptoms (cough, sore throat, conjunctivitis) and a longer duration (5–12 days vs 3–8 days for rotavirus). Fever tends to be higher with rotavirus in children. The test helps distinguish the two quickly.

When to Seek Medical Care

If you or your child has diarrhea with signs of dehydration — dry mouth, excessive thirst, sunken eyes, decreased urination, lethargy — seek care promptly. While the stool test provides reassurance, the cornerstone of treatment remains oral rehydration. In severe cases, intravenous fluids may be needed. Most viral gastroenteritis resolves on its own within a week.