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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 Test | Sensitivity (%) | Specificity (%) |
|---|---|---|
| Fecal Leukocytes | 55-70 * | 63-87 * |
| Lactoferrin | 71-92 * | 79-100 * |
| C. difficile cytotoxic assay | 70-90 | 100 |
| C. difficile PCR assay | 100 | 96 |
| C. difficile EIA (toxin A or B) | 61-94 | 96-99 |
| C. difficile EIA (GDH) | 100 | 61-73 |
| C. difficile LAMP assay | 98 | 98 |
| Campylobacter EIA | 75-100 | 97-98 |
| Shiga toxin EIA | 92-100 | 98-100 |
| Giardia EIA | 94-99 | 100 |
| E. histolytica EIA | 82 | 99 |
| Multiplexed PCR assays | 87-100 | 93-100 |
EIA, Enzyme immunoassay; GDH, glutamate dehydrogenase; L
