Viral Gastroenteritis Workup

Updated: Jan 08, 2018
  • Author: Brian Lin; Chief Editor: Burt Cagir, MD, FACS  more...
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Laboratory Studies

General laboratory evaluation

In most cases that fit the clinical features of viral gastroenteritis, laboratory tests are not indicated.

If bacterial or protozoal infection is suspected, stool studies for occult blood, white blood cell (WBC) count, microscopy for protozoa, C difficile toxin, Giardia lamblia by enzyme immunoassay (EIA), or bacterial culture may be indicated.

Consider investigating patients with low-grade fever, nausea, vomiting, abdominal pain, and extreme dehydration by evaluating serum electrolytes, urea, creatinine, amylase, complete blood cell (CBC) count, and abdominal imaging studies.

Blood cultures should be obtained in patients with high fevers or who appear systemically ill.

Stool cultures are not performed for most patients who do not have severe illness or high-risk comorbidities, because most infectious cases of acute diarrhea are self-limited and of viral etiology, and the rate of positive stool cultures in all-comers with acute diarrhea is generally low. [25]  When stool cultures are obtained in patients with acute diarrhea, it is to identify a potential bacterial pathogen and determine the potential for complications and treatment decisions.

Polymerase chain reaction (PCR) for enteropathogen detection in stool of patients with diarrhea is available. Cost effectiveness in specific communities remains to be determined. [26]

Japanese researchers have developed a multiplex real-time PCR assay to detect human enteric viruses other than norovirus ("non-NoV" gastroenteritis viruses) conducted separately from norovirus testing that have the potential to deal with two types of epidemiologic investigations: regular surveillance of infectious gastroenteritis and urgent testing when gastroenteritis outbreaks occur. [27]

In a systematic literature review, Lee et al used pooled data to calculate median incubation periods for astrovirus (4.5 days), norovirus genogroups I and II (1.2 days), sapovirus (1.7 days), and rotavirus (2.0 days). [28]

Diagnosis of rotavirus infection

Rapid antigen testing of the stool, either by EIA (>98% sensitivity and specificity) or latex agglutination tests (less sensitive and specific as compared to EIA), is used to aid in the diagnosis of rotavirus infection.

Expect antirotavirus antibodies (ie, immunoglobulin M, immunoglobulin A) to be excreted in the stool after the first day of illness. Antibody tests can remain positive for 10 days after primary infection and longer after reinfection; therefore, they can be used as an adjunct to diagnosis.

Diagnosis of calicivirus infection

In epidemics, save stool and emesis specimens for evaluation by public health officials. Polymerase chain reaction is valuable in both the outbreak setting and the sporadic case setting.

Researchers have cloned several of the caliciviruses and placed the genome in a baculovirus that produces unlimited amounts of recombinant calicivirus capsid protein. Enzyme immunoassays for serum antibody and stool antigen have been developed using this antigen source.

A modification to PCR has allowed many of the various strains of caliciviruses to be recognized with just a few primers (broadly reactive reverse-transcription polymerase chain reaction). These primers are directed at a region of the genome that is common to many of the strains of calicivirus. This has been an important tool for identifying caliciviruses as the most common cause of epidemic viral gastroenteritis.

Fecal viral concentration of norovirus correlates with duration of illness. As in most viral infections, active viral replication determines clinical disease. High fecal viral concentrations suggest the need for both aggressive fluid replacement and stringent infection control measures. [29]