Diagnosis The diagnosis of diphtheria is based on clinical signs and symptoms plus laboratory confirmation. Respiratory diphtheria should be considered in patients with sore throat, pharyngeal exudates, and fever. Other symptoms may include hoarseness, stridor, or palatal paralysis. The presence of a pseudomembrane should prompt consideration of diphtheria. Once a clinical diagnosis of diphtheria is made, diphtheria antitoxin should be administered as soon as possible. Laboratory diagnosis is based either on cultivation of C. diphtheriae or toxigenic C. ulcerans from the site of infection or on the demonstration of local lesions with characteristic histopathology. .
