The diagnosis is primarily clinical. In isolated anticholinergic toxicity, routine laboratory studies should be normal, and routine toxicology screening is often of little value. Nonetheless, electrolytes, glucose, creatine phosphokinase, and pulse oximetry should be obtained. The differential diagnosis includes viral encephalitis, Reye syndrome, head trauma, other intoxications, neuroleptic malignant syndrome, delirium tremens, acute psychiatric disorders, and sympathomimetic toxicity.