What is the primary method for diagnosing C. difficile infection?

The primary method for diagnosing Clostridioides difficile infection (CDI) is through the detection of toxins A or B in stool samples. This is because these toxins are key indicators of an active infection, as they are produced by the bacteria and are responsible for the diarrhea and inflammation associated with CDI. Stool tests are able to specifically identify the presence of these toxins, making them a reliable diagnostic tool.

Visualizing pseudomembranes via endoscopy can be an ancillary method to support the diagnosis but is not routinely performed for diagnosis. Endoscopy is typically reserved for severe cases where colitis is suspected, as it carries risks and is not necessary for most routine CDI evaluations.

Detecting C. difficile in blood cultures is not a standard diagnostic approach since the bacteria are primarily present in the gut. Blood cultures are generally not useful for diagnosing gastrointestinal infections like CDI, as C. difficile typically does not invade the bloodstream in the way other pathogens might.

Thus, the emphasis on stool testing for toxins A and B aligns with current guidelines and practices for effectively diagnosing C. difficile infection.