5-Hydroxyindoleacetic Acid (5-HIAA), 24-Hour Urine

The 5-Hydroxyindoleacetic Acid (5-HIAA), 24-Hour Urine test contains 1 test with 3 biomarkers.

5-Hydroxyindoleacetic Acid (5-HIAA), 24-Hour Urine, with Creatinine

Patient Preparation: Patient should avoid food high in indoles: avocado, banana, tomato, plum, walnut, pineapple, and eggplant.

Collection Instructions : Collect 24-hour urine with 6N HCL to maintain a pH below 3. Urine without preservative is acceptable if pH is below 6 and the sample is shipped frozen. Keep urine refrigerated during collection if preservative is not used. Shipping refrigerated acceptable, shipping frozen acceptable. Record 24-hour urine volume on test request form and urine vial. Record patient's age on test request form and urine vial.

Clinical Significance: 5-HIAA is the end product of serotonin (5-hydroxytryptophan) and tyrptophan metabolism. Patients with carcinoid tumors of the midgut, e.g., ileum, produce high concentrations of 5-HIAA. Patients with carcinoid tumors of the foregut and hindgut may produce little or no 5-HIAA or do so intermittently.

Limitations: Patients with renal disease may display falsely decreased results. Urinary 5-HIAA is increased in patients with malabsorption disorders who also display a larger concentration of urinary tryptophan metabolites. Urinary 5-HIAA is increased in patients with intestinal obstruction and with some noncarcinoid islet cell tumors. Carcinoid syndrome may not cause elevated results, especially if the patient does not have diarrhea.