Consider testing patients with unexplained and new-onset ≥3 unformed stools within 24 hours
Institutions should have an agreed protocol using a stool toxin test as part of a multistep algorithm (e.g. glutamate dehydrogenase [GDH] plus toxin; GDH plus toxin, arbitrated by nucleic acid amplification test [NAAT])
or NAAT plus toxin) rather than a NAAT alone for all specimens received in the clinical laboratory when there are no preagreed institutional criteria for patient stool submission (Figure 2) (weak recommendation, low quality of evidence).
or NAAT plus toxin) rather than a NAAT alone for all specimens received in the clinical laboratory when there are no preagreed institutional criteria for patient stool submission (Figure 2) (weak recommendation, low quality of evidence).

C.<unk>  toxin assay
Sn 63-94%, Sp 75-100%
Culture
Positive culture only means C.<unk>  present, not necessarily that it is causing disease
Sn 63-94%, Sp 75-100%
Positive culture only means C.<unk>  present, not necessarily that it is causing disease

For patients with suspected<unk>  associated diarrhea <unk> AD)
Low suspicion
Send stool for C.<unk>  toxin assay
Positive → treat (no further testing indicated)
Negative → do not treat (no further testing indicated)
High suspicion
Send stool for C.<unk>  toxin assay AND treat empirically
Positive → treat (no further testing indicated)
Negative → Consider discussion with ID (false negative tests may occur); eval for other causes of diarrhea
Send stool for C.<unk>  toxin assay
Positive → treat (no further testing indicated)
Negative → do not treat (no further testing indicated)
Positive → treat (no further testing indicated)
Negative → do not treat (no further testing indicated)
Send stool for C.<unk>  toxin assay AND treat empirically
Positive → treat (no further testing indicated)
Negative → Consider discussion with ID (false negative tests may occur); eval for other causes of diarrhea
Positive → treat (no further testing indicated)
Negative → Consider discussion with ID (false negative tests may occur); eval for other causes of diarrhea
Never a need for repeat testing within 7 days of a previous test
NO NEED to repeat positive tests as symptoms resolve as a “test of cure”
NO NEED to repeat test soon after initial negative test (more likely to be a false positive test than a true positive test)
Leukocytosis with a white blood cell count of ≥15000 cells/mL
Serum creatinine level >1.5 mg/dL
Serum lactate levels >2.2 mmol/l
Mental status changes
WBC ≥35,000 cells/mm3 or <2,000 cells/mm3
Patient requiring ICU admission
End organ failure (mechanical ventilation, renal failure, etc.)
Hypotension with or without required use of vasopressors
Ileus or significant abdominal distention
Megacolon
Clostridium difficile
Viral 
Salmonella
Bacterial
Campylobacter jejuni
Campylobacter
Yersinia enterocolitica
Shigella