The stool toxin assay is the gold standard for confirming Clostridium difficile infection (CDI) in surgical patients, as it directly detects the presence of toxins A and B produced by the bacteria. These toxins cause the characteristic colitis and diarrhea associated with CDI, which is common in post-operative patients who have received antibiotics. Blood cultures and urine antigen tests do not detect C. difficile, and chest X-rays are not relevant for gastrointestinal infections. Rapid and accurate identification via stool toxin assay enables timely treatment, which is critical to prevent severe complications like pseudomembranous colitis and sepsis in surgical patients.

Reference: Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 9th Edition.