Diagnosis of C. difficile infection

Early diagnosis and treatment of CDI are crucial in preventing complications and controlling the spread of infection. CDI is a clinical diagnosis derived by considering patient risk factors, symptom progression, and data from laboratory tests. There are a number of different laboratory tests and algorithms that can be used to aid in the diagnosis of CDI. Because C. difficile is a toxin-mediated disease, a laboratory must include a test for C. difficile toxin in any testing scheme. Due to high levels of asymptomatic carriage for toxinogenic C. difficile among patients in hospitals and long term care facilities (up to 50% carriage rate) it is essential that only specimens from clearly symptomatic patients are submitted for laboratory testing.

Differential diagnosis of C. diff infection

The symptoms of CDI include:

• Watery or loose stools more than three times/day
• Fever
• Abdominal pain and distension
• Leukocytosis

The severity of CDI may range from mild (uncomplicated diarrhea) to moderate (fever, profuse diarrhea, abdominal pain, and leukocytosis) and, in extreme instances, severe (toxic megacolon, dehydration, and sepsis) disease.

The differential diagnosis for CDI includes⁵

• Benign or simple antibiotic-associated diarrhea
• Acute and chronic diarrhea caused by other enteric pathogens
• Adverse drug reactions (other than antibiotics)
• Ischemic colitis
• Idiopathic inflammatory bowel diseases
• Intra-abdominal sepsis

Important, updated information on diagnostic tests and how to choose the ones for your facility