The diagnosis is confirmed if the increased excretion of 5-HIA acid in urine of 24 hours exceeds 10 mgs. However, before samples are taken the patient should take the precaution to restrict consumption of serotonin rich foods such as bananas, grapes, pineapple, tomatoes, plums, eggplant, kiwi fruit and nuts for 3 to five days. The patient must also suspend cough syrups, levodopa, methysergide, paracetamol, NSAIDs, and caffeine for the same period. If these precautions are not taken falsely elevated results are likely.
El diagnóstico se confirma si la excreción aumentada del ácido 5-HIA en orina de 24 horas excede los 10 mg, teniendo la precaución de restringir por los 3-5 días previos al estudio alimentos ricos en serotonina banano, uva, piña, tomates, ciruelas, berenjena, kiwi, nueces y suspender los jarabes para la tos, levodopa, metisergida, paracetamol, AINEs y cafeína que dan cifras falsamente elevadas.