Serotonin Syndrome - Diagnosis

Diagnosis

There is no laboratory test for serotonin syndrome. Therefore diagnosis is by symptom observation and investigation of the patient's history. Several diagnostic criteria have been proposed. The first rigorously evaluated criteria were introduced in 1991 by Harvey Sternbach, a professor of psychiatry at UCLA. Researchers in Australia later developed the Hunter Toxicity Criteria Decision Rules, which have better sensitivity and specificity, 84% and 97%, respectively, when compared with the gold standard of diagnosis by a medical toxicologist. As of 2007, Sternbach's criteria were still the most commonly used.

The most important symptoms for diagnosing serotonin syndrome are tremor, akathisia, or clonus (spontaneous, inducible and ocular). Physical examination of the patient should include assessment of deep-tendon reflexes and muscle rigidity, the dryness of the oral mucosa, the size and reactivity of the pupils, the intensity of bowel sounds, skin color, and the presence or absence of sweating. The patient's history also plays an important role in diagnosis, investigations should include enquries about the use of prescription and over-the-counter drugs, illicit substances, and dietary supplements, as all these agents have been implicated in the development of serotonin syndrome. To fulfill the Hunter Criteria, a patient must have taken a serotonergic agent and meet one of the following conditions:

• Spontaneous clonus, or
• Inducible clonus plus agitation or diaphoresis, or
• Ocular clonus plus agitation or diaphoresis, or
• Tremor plus hyperreflexia, or
• Hypertonism plus temperature > 38 °C (100 °F) plus ocular clonus or inducible clonus