Tests
1st tests to order
clinical diagnosis
Test
Viral gastroenteritis is usually a clinical diagnosis and no investigations are needed.
Result
self-limiting watery diarrhea, vomiting, or both, with or without fever, malaise, and anorexia
Tests to consider
basic metabolic profile
Test
Perform if moderate or severe volume depletion.
Result
sodium levels may be elevated, or low in very severe volume depletion with free water repletion; possible hypokalemia (or hyperkalemia if dehydration leads to renal failure); metabolic acidosis
renal function
Test
Perform if moderate or severe volume depletion.
Result
BUN, creatinine, or ratio may be elevated.
stool rapid antigen testing
Test
Samples for stool latex agglutination or enzyme immunoassay for viruses are sent for rapid diagnosis in cases of outbreaks.[19] Clinicians may consider ordering this test in patients with moderate to severe illness.[20] It has >95% sensitivity and specificity.
Result
may be positive for rotavirus or calicivirus
stool reverse transcriptase polymerase chain reaction (RT-PCR) or multiplex PCR
stool viral culture
Test
Not a routine test but may be needed in rare cases. The most specific test for identification of viral pathogens.
Result
may identify a specific virus
stool electron microscopy
Test
Not a routine test but may be needed in cases in which diagnosis is difficult.
Result
may identify a specific virus
stool for culture, ova, and parasites
Test
Order if symptoms are atypical and a bacterial or parasitic etiology is suspected (e.g., bloody diarrhea, high fever, or tenesmus).
Stool ova and parasite and WBC detection under microscopy can be an initial test under these circumstances.
However, do not order a comprehensive stool ova and parasite microscopic exam on patients presenting with diarrhea of less than 7 days’ duration who have no immunodeficiency or no history of living in or traveling to endemic areas where gastrointestinal parasitic infections are prevalent.[23]
The comprehensive ova and parasite microscopic exam often requires submission of multiple stool samples. It is labor intensive, requires significant expertise to perform, and typically has lower sensitivity when compared with other available tests.[23]
Result
may identify enteropathogenic bacteria or show parasitic infection
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