5.2 Diagnostic criteria
Serotonin syndrome is a clinical diagnosis based primarily by evaluation of the patient’s medical history (use of serotonergic drugs or illicit substances, change in dose or addition of new drugs) and a physical examination 2–4. No biomarkers have been identified for serotonin syndrome, although certain nonspecific laboratory abnormalities, such as leukocytosis, low bicarbonate level, elevated creatinine level, and elevated transaminases, have been reported4.
Several diagnostic criteria have been suggested for the categorization of serotonin syndrome. The most accurate are the Hunter Serotonin Toxicity Criteria that have replaced the older Sternbach Criteria. The Hunter Criteria have 84% sensitivity and 97% specificity for moderate and severe serotonin syndrome when compared to the diagnostic gold standard for serotonin syndrome: a diagnosis by a medical toxicologist. Mild cases of serotonin syndrome are difficult to distinguish from numerous other medical conditions and side effects, which is why the Hunter Criteria cannot be used for this 3,8.
The Hunter Serotonin Toxicity Criteria appear in figure 13 below.