CDI is traditionally diagnosed by a variety of methods, including a review of past medical history, an examination of signs and symptoms, and laboratory-based testing. In rare cases, a sigmoidoscopy or colonoscopy may be used to examine the colon. If complications develop, abdominal imaging studies may be used, such as X-rays and/or CT-scans. Since laboratory tests are usually necessary to make the diagnosis of CDI, this course will concentrate on the various laboratory-based tests that are used to confirm and identify infections with C. difficile.
There are several challenges to the diagnosis of CDI. The following are key diagnostic challenges for the clinical lab to positively and accurately identify a CDI:
Carriers: Studies have shown that CDI, in some cases, may not cause symptoms, or the infection can be a mild self-limiting infection. In addition, an individual can carry the C Diff organism but diarrhea may be caused by another organism or condition. These cases can present a diagnostic challenge relative to being able to accurately identify and treat patients with true CDI versus those patients who are carriers and may not need treatment.
Lab test sensitivity and over-diagnosis: Spores produced by C diff are very stable and can remain in the patient's intestine for some time. Some laboratory tests are very sensitive and can detect low levels of C diff in the patient specimen, but the level may not be clinically relevant. This can lead to the over-diagnosis of CDI and a low positive predictive value (PPV) for certain tests.
