Tests
1st tests to order
stool culture and sensitivity
Test
Use stool culture and sensitivity kit.
Diarrheal stool is the preferred specimen over formed stool or swab to detect diarrheal sickness, except in children where swab is acceptable when there is sufficient feces on the swab.[30]
Stool cultures usually take a longer time to process and may fail to detect the causative agent.[30] Negative stool workups are very likely, and in the acute TD clinical scenario, a course of empiric therapy should be tried.
Not necessary for nonsevere TD or if traveler has not tried a course of appropriate antibiotic therapy.
Result
identifies specific bacterial etiology with sensitivities
multipathogen molecular diagnostic (polymerase chain reaction)
protozoal stool antigens
Test
Performed for persistent diarrhea (usually >14 days).
Reagents are commercially available for Cryptosporidium species, Entamoeba histolytica, and Giardia duodenalis.
Result
identifies Giardia, Cryptosporidium, E histolytica
Tests to consider
stool ova and parasite exam
Test
Performed for persistent diarrhea (usually >14 days). The Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM) guidelines suggest considering testing for parasites in patients having persistent diarrhea for >7 days.[30]
Use stool ova and parasite (O+P) collection kit.
Cryptosporidium is easily missed on stool O+P.
Cryptosporidium stool antigen test is specific for this organism.
Not as reliable as stool antigen test for detection of Giardia.
Do not order a comprehensive stool ova and parasite microscopic exam on patients presenting with diarrhea of <7 days’ duration who have no immunodeficiency or no history of living in or traveling to endemic areas where gastrointestinal parasitic infections are prevalent.[31]
This exam often requires submission of multiple stool samples. It is labor intensive, requires expertise to perform, and typically has lower sensitivity when compared to other available tests.[31]
Result
identifies specific parasitic etiology (a negative acid-fast stain helps to exclude Cryptosporidium and Cyclospora)
Clostridioides difficile stool toxin
Test
Recommended in the scenario of inflammatory colitis in a returning traveler with recent antibiotic exposure.
Result
identifies C difficile
colonoscopy, endoscopy, and biopsy
Test
Recommended for chronic diarrhea to rule out structural or organic disease.
Result
identifies inflammatory bowel disease, colon cancer, microscopic colitis, tropical sprue and malabsorptive conditions, and celiac disease
hematology, blood chemistries, serology
Test
C-reactive protein, erythrocyte sedimentation rate, and liver function tests identify organic disease.
White blood cells, and particularly eosinophilia, are indicative of extra-intestinal protozoa (e.g., Strongyloides).
Celiac serologies considered depending on traveler family history and symptoms.[6]
Result
test based on individually derived differential diagnosis
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