How is infectious diarrhea diagnosed

What tests are used to diagnose infectious diarrhea? 

Although routine stool cultures for common bacterial agents ( E. coli, Salmonella, Shigella, and Campylobacter ) and microscopy (for ova and parasites) can be useful in clinical practice, newer tests have emerged that are faster, more sensitive, and less labor intensive. Enzyme immunoassays (EIAs) for pathogenic antigens have become the tests of choice for many protozoa, viruses, and some bacterial products. Testing for viral pathogens is usually not clinically indicated because of the self-limited nature of the infection. PCR techniques have become widespread for a number of pathogens, and commercially available kits that perform PCR assays for multiple pathogens from a single specimen (multiplexed PCR) have recently been approved by the Food and Drug Administration and may become the test of choice for undifferentiated diarrhea.

Sensitivity and Specificity for Common Microbiological Tests Used in the Evaluation of Infectious Diarrhea

Stool TestSensitivity (%)Specificity (%)
Fecal Leukocytes55-70 *63-87 *
Lactoferrin71-92 *79-100 *
C. difficile cytotoxic assay70-90100
C. difficile PCR assay10096
C. difficile EIA (toxin A or B)61-9496-99
C. difficile EIA (GDH)10061-73
C. difficile LAMP assay9898
Campylobacter EIA75-10097-98
Shiga toxin EIA92-10098-100
Giardia EIA94-99100
E. histolytica EIA8299
Multiplexed PCR assays87-10093-100

EIA, Enzyme immunoassay; GDH, glutamate dehydrogenase; L


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