THE 24-HOUR URINARY 5-HIAA: A SIMPLE TEST WITH A COMMON PITFALL. Margaret L Burks, MD, Shichun Bao, MD, PhD

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1 AACE Clinical Case Reports Rapid Electronic Articles in Press Rapid Electronic Articles in Press are preprinted manuscripts that have been reviewed and accepted for publication, but have yet to be edited, typeset and finalized. This version of the manuscript will be replaced with the final, published version after it has been published in the print edition of the journal. The final, published version may differ from this proof.. Case report EP15794.CR THE 24-HOUR URINARY 5-HIAA: A SIMPLE TEST WITH A COMMON PITFALL Margaret L Burks, MD, Shichun Bao, MD, PhD From: Vanderbilt University Medical Center Running title: Pitfalls of the Urinary 5-HIAA Test Correspondence address: Margaret L Burks MD Vanderbilt University Medical Center st Avenue South, Nashville, TN margaret.l.burks@vanderbilt.edu

2 Abstract Objective: 5-hydroxyindoleaceticacid (5-HIAA) is the principal metabolite of serotonin and the quantitative urinary excretion of 5-HIAA is the most useful way to diagnose serotonin overproduction by carcinoid tumors. The test carries a high specificity, however, many serotonin-rich foods such as pineapple, banana, kiwi, and walnuts will also increase urinary 5-HIAA excretion. We present a case which demonstrates that consumption of these foods prior to the 24 hour collection will falsely elevate the test results. Methods: Case report with literature review. Results: A 39 year old female presented to endocrine clinic with episodes of hot flushing. She had no diarrhea, diaphoresis, skin rash, muscle weakness, or purple striae. Her primary doctor was concerned for carcinoid syndrome after a 24 hour urine 5-HIAA level was elevated to 22.7 mg/24 hours (normal <6 mg/ 24hours). After negative CT and octreotide scans, it was felt that the patient s 24 hour urine 5-HIAA test was falsely elevated due to dietary intake. She was instructed to avoid serotonin-rich foods prior to her repeat urine collection. The subsequent 24 hour urine test returned within normal limits. She indeed did not have carcinoid syndrome. The patient continued to have flushing episodes of feeling short winded and tremulous which resolved with treatment for anxiety. Conclusion: To prevent false positive results and avoid unnecessary testing and imaging, serotonin-rich foods should be avoided for at least 12 hours prior to urine collection. Biochemical tests for diagnosis of clinical syndromes should be interpreted with understanding of the potential for false positive results.

3 Abbreviations: 5-HIAA = 5-hydroxyindoleaceticacid; ARUP = Associated Regional and University Pathologists, Inc; CGA = chromogranin A ; CT = computed tomography; HPLC = high performance liquid chromatography. Introduction 5-hydroxyindoleaceticacid (5-HIAA) is the principal metabolite of serotonin. The quantitative measurement of 24-hour urinary excretion of 5-HIAA is the most useful way to diagnose serotonin overproduction by mid-gut carcinoid tumors (1, 2), with a sensitivity and specificity around 70% and 90%, respectively (3). Case Presentation A 39-year-old female with a past medical history of anxiety presented to endocrine clinic with episodes of hot flushing described as warmth and erythema of the face, chest, and upper arms. The flushing episodes happened 2-3 days in a row, approximately once every 1-2 weeks. She denied associated diarrhea, diaphoresis, skin rash, muscle weakness, or purple striae. The flushing was worse during episodes of anxiety or stress. She had no prior history of hypertension and no family history of neuroendocrine disorder. She was a former smoker, but had quit smoking for 3 years. She consumed one regular coffee every morning. She denied consumption of alcohol. Her medication list included a multivitamin and acetaminophen as needed for pain. Physical exam was unremarkable aside from mild erythema of the face, neck, chest and upper extremities. She was afebrile with mildly elevated blood pressure (147/76 mmhg) and a normal heart rate (86 bpm). The patient was referred to endocrine clinic with the above symptoms after a 24-hour urine 5-HIAA test collected in primary care clinic was elevated to 22.7 mg/24 hrs (normal <6 mg/24hrs). Other labs included a normal serum ACTH, serum cortisol, plasma metanephrine, normetanephrine, and thyroid

4 hormone levels. Abdominal computed tomography (CT) scan following laboratory results was unremarkable. A 24-hour urine 5-HIAA was repeated and again elevated to 14.4 mg/24 hours. The patient then underwent an octreotide scan to evaluate for carcinoid tumor. This scan showed no evidence of a somatostatin-receptor-avid tumor. It was after the negative CT and octreotide scans that we realized the sampling conditions of the first two 24-hour urine collections were not respected. This was verified with the patient. She had not been told to avoid tryptophan/serotonin-rich foods, caffeine, or acetaminophen prior to the 24-hour urine collection. The results could thus be falsely elevated due to interfering substances. The patient was then instructed to avoid tryptophan/serotonin-rich foods, caffeine, and acetaminophen for 2-3 days prior to the third 24-hour urine 5-HIAA measurement. After following these instructions, the result was normal (4.8 mg/24 hours). Her blood serotonin level was also normal. She continued to have flushing episodes of feeling short winded and tremulous. She was treated with sertraline and alprazolam for presumed panic attack, which alleviated her symptoms. Discussion The 24-hour urine 5-HIAA test is the most useful test to diagnose primary mid-gut (jejunoileal, appendiceal, and ascending colon) carcinoid tumors, which produce the highest levels of serotonin. The test is generally not useful to diagnose carcinoid tumors in the fore-gut (gastro duodenal, bronchus) and hind-gut (transverse, descending and sigmoid colon, rectum, genitourinary), as those tumors only rarely secrete serotonin, and imaging studies should be pursued to search for a carcinoid tumor. Patients with foregut and hindgut carcinoid tumors usually do not present with flushing (4). False positive 24-hour urine 5-HIAA results may be induced by the ingestion of tryptophan/serotonin-rich foods (pineapple, banana, kiwi, plum, tomato, avocado, walnut, eggplant, hickory nut, etc.), and certain medications and supplements such as acetaminophen, nicotine, and caffeine (5,6). It is important that these substances be avoided for 24 to 72 hours prior to the 24-hour urine

5 collection. Most clinical guidelines indicate avoidance at least 24 hours prior to collection (4). Mayo Medical Laboratories recommends 48 hours prior, while Associated Regional and University Pathologists, Inc. (ARUP Laboratories) states that these substances should be avoided for 72 hours prior to the 24-hour urine collection (7,8). Several assays are available to measure 24-hour urine 5-HIAA, including high performance liquid chromatography (HPLC, used by ARUP Laboratories), liquid chromatography-mass spectrometry (used by Mayo Medical Laboratories), thin-layer and gas chromatography, and enzyme immunoassay. HPLC is the most commonly utilized and recommended methodology and was the laboratory assay used in this case (7,8,9). Interference substances that can cause false positive 24-hour urine 5-HIAA results seem to be similar across metrologies rather than assay related (7,8). Other assays measuring serotonin in whole blood, plasma, platelets, and urine have been described in the literature; however, these assays have their own limitations. The sensitivities and specificities of these assays have not been well established, and therefore cannot be recommended as the standard diagnostic tests for carcinoid syndrome. Blood serotonin can be affected by changes in platelet counts and saturation of platelets with serotonin, as well as by consuming tryptophan/serotonin-rich foods (10). Urinary and platelet serotonin levels are not affected by ingestion of tryptophan/serotonin-rich foods and can provide helpful adjunctive information in patients with carcinoid tumors that secrete only small amounts of serotonin (5). However, urinary serotonin levels lack sensitivity, and platelet serotonin levels are age dependent (2,10,11). Platelet serotonin levels have been reported to be about 30% lower in the elderly compared to adults and children (11). Chromogranin A (CGA) is a protein that is stored and released in a variety of well-differentiated neuroendocrine tumors, including carcinoids. False positive elevations of CGA may occur in patients with impaired hepatic and renal function and in those taking proton pump inhibitors (12). Due to its low specificity, CGA cannot be recommended as the screening test for carcinoid syndrome.

6 The correct sampling conditions of biochemical tests must be respected before submitting to sophisticated and expensive imaging methods. Once the biochemical diagnosis of the carcinoid syndrome is confirmed, usually by an elevated 24-hour urine 5-HIAA, the tumor can be localized and staged by CT and octreotide scan. Conclusions Biochemical tests for diagnosis of clinical syndromes are very helpful, but each test must be interpreted and approached with caution and understanding of potentially dangerous pitfalls in interpretation. Acknowledgements We thank Dr. Jessica Thomas and Dr. Alison Woodworth from the Department of Pathology, Microbiology and Immunology at Vanderbilt University Medical Center for their helpful input regarding 24-hour urine 5-HIAA assay. References 1. Grahame-Smith DG. The carcinoid syndrome. London: William Heinemann Medical Books LTD, Feldman JM. Urinary serotonin in the diagnosis of carcinoid tumors. Clin Chem. 1986; 32: O Toole D, Grossman A, Gross D, et al. ENETS consensus guidelines for the standards of care in neuroendocrine tumors: biochemical markers. Neuroendocrinology. 2009; 90: Feldman JM. Carcinoid tumors and syndrome. Semin Oncol. 1987; 14: Kema IP, Schellings AM, Meiborg G, et al. Influence of a serotonin and dopamine rich diet on platelet serotonin content and urinary excretion of biogenic amines and their metabolites. Clin Chem. 1992; 38:

7 6. Feldman JM and Lee EM. Serotonin content of foods: effect on urinary excretion of hydroxyindoleacetic acid. Am J Clin Nutr. 1985; 42: Hydroxyindoleacetic Acid (5-HIAA), 24 Hour, Urine. Mayo Medical Laboratories. Mayo Foundation for Medical Education and Research Web. 6 July < 8. "5-Hydroxyindoleacetic acid (HIAA), Urine." Arup Laboratories Laboratory Test Directory. Arup Laboratories Web. 6 July < 9. Kema IP, de Vries EG, Muskiet FA. Clinical chemistry of serotonin and metabolites. J Chromatogr B Biomed Sci Appl. 2000; 747: Allen KR, Degg TJ, Anthoney DA, et al. Monitoring the treatment of carcinoid disease using blood serotonin and plasma 5-hydroxyindoleacetic acid: three case examples. Ann Clin Biochem. 2007; 44: Kema IP, de Vries EG, Schellings AM, et al. Improved diagnosis of carcinoid tumors by measurement of platelet serotonin. Clin Chem. 1992; 38: Marotta V, Nuzzo V, Ferrara T, et al. Limitations of chromogranin A in clinical practice. Biomarkers. 2012; 17: