Clostridioides difficile Diagnostic Testing

Timely and accurate diagnosis of Clostridioides difficile infection (CDI) is essential but challenging to implement consistently. As diarrhoea is such a common symptom, there is a tendency to miss possible CDI diagnoses, especially but not only in community-onset cases. Hospital-onset diarrhoea affects about 1 in 20 patients each day during their stay, with the great majority having multiple potential causes for their diarrhoea. Tests are available to detect the organism, its toxins or its DNA, and each approach has both strengths and weaknesses. No single test is ideal, and so use of a screening test and then a confirmatory test is recommended. Detection of toxin in faeces is the most specific test but may lack sensitivity. Nucleic acid amplification tests to detect toxin genes are sensitive but markedly over-diagnose CDI if used alone. Diagnostic stewardship aims to optimise the use of microbiological diagnostics to guide decision making. Multiple strategies have been explored to reduce misdiagnosis of C. difficile colonisation as CDI, but the relative efficacies of such approaches are not clear. Over-enthusiastic implementation of such approaches risks missing real CDIs. Improved testing options for CDI are needed, including reliable near-to-patient tests and ideally assays that can identify those at higher risk of poor outcomes, especially recurrent CDI.