In suspecting a C. difficile infection, which stool pattern meets the diagnostic criterion?

• A. Two or more formed stools in 24 hours
• B. Three or more unformed stools in 24 hours
• C. One loose stool in 24 hours
• D. Diarrhea lasting more than 72 hours

Answer: (B)

The main concept is how diarrhea is defined for suspecting C. difficile infection: three or more unformed stools within a 24-hour period. Unformed stool means watery or loose stool, not solid formed stool. This pattern signals diarrhea, which is the trigger for evaluating CDI. The other patterns don’t meet the diagnostic threshold because they involve either formed stools, too few occurrences, or are focusing on duration rather than stool consistency and frequency. Three or more unformed stools in 24 hours best fits the diagnostic criterion for CDI suspicion.