Stool Test for Rotavirus
The stool test for rotavirus is an enzyme immunoassay (EIA) that detects rotavirus antigen in fecal specimens—this is the most widely available, rapid, and practical diagnostic method for clinical use and surveillance. 1, 2
How the Test Works
The EIA detects an antigen common to all group A rotaviruses (the primary cause of human disease) directly from stool samples. Rotavirus is shed in extremely high concentrations in stool during acute gastroenteritis (approximately 10^12 viruses per gram), making detection straightforward 1.
Test Characteristics
Clinical Performance:
- Sensitivity: 90-100% when compared to electron microscopy 1, 3
- Specificity: 99-100% in most commercial kits 1, 4
- The test is inexpensive, easy to use, and provides rapid results 1, 2
Important Caveats:
- Newborns and breastfeeding children have particularly high false-positive rates 3
- One immunochromatographic test showed poor specificity (54.3%), so not all rapid tests are equally reliable 4
- The test is most useful during rotavirus season (typically winter-spring in temperate climates); confirmatory testing should be performed when rotavirus would be unusual (e.g., summer outbreaks in children or any adult cases) 3
Specimen Collection
Standard specimen: Bulk stool sample is traditional and preferred 1, 2
Alternative specimen: Rectal swabs are acceptable when bulk stool collection is not feasible, showing 95% sensitivity and 92-100% specificity compared to bulk stool 5. This is particularly useful during outbreak investigations when immediate sampling is needed.
Sample handling: Only small amounts of stool are required, and samples may be frozen before testing 3
When to Order the Test
Laboratory confirmation is necessary because rotavirus gastroenteritis cannot be distinguished clinically from gastroenteritis caused by other pathogens 1, 2. Testing is particularly useful for:
- Reliable surveillance programs
- Making decisions about antimicrobial use (avoiding unnecessary antibiotics)
- Infection control purposes in healthcare settings 2
- Outbreak investigations
Alternative Testing Methods
Research/specialized settings only:
- RT-PCR (reverse transcription-polymerase chain reaction) - more sensitive and specific than EIA but not routinely available 2, 6
- Electron microscopy
- RNA electrophoresis
- Nucleic acid hybridization
- Sequence analysis
- Viral culture 1, 2
Serologic testing: Detection of rotavirus-specific IgG and IgA antibodies can confirm recent infection but is used primarily in research and vaccine trials, not for acute diagnosis 1, 2
Note: The 2017 IDSA guidelines list both culture/EIA and NAAT (nucleic acid amplification testing) as acceptable methods for rotavirus detection 7, reflecting the evolution toward molecular diagnostics, though EIA remains the workhorse in most clinical laboratories.