Background/Aims: Carcinoid syndrome (flushing, diarrhea, carcinoid heart disease and bronchospasm) is a complication of small intestinal neuroendocrine tumors (SI-NETs). These rare tumors often have metastasized to the liver at time of diagnosis. Vasoactive substances produced by these tumors are responsible for the syndrome, serotonin being the most important. 5-hydroxyindole acetic acid (5-HIAA), the degradation product of serotonin, measured in a 24 hour urine sample is considered the cornerstone for diagnosis and follow up in patients with carcinoid syndrome. This test is troublesome for both patients and health care professionals. In this study, we wanted to investigate if urine collected over a shorter interval can replace 24 hour urine sampling.
Patients and methods: Urine samples obtained from 34 patients were analyzed using High-performance liquid chromatography. All patients had two paired urine samples, one morning sample and one 24 hour sample, collected the same day. The morning samples were taken from the overnight collection of urine (8 hours) obtained during the 24 hour collection.
Results: Median collection time for the morning sample was 8.3 hours [7 – 10 hours]. Morning U5-HIAA values were compared to 24 hour U5-HIAA, and no difference was found (Wilcoxon’s signed rank test, P=0.446). There was also a significant correlation between the two samples by linear regression (R=0.973, P<0.001).
Conclusion: U-5HIAA sample collected during a nightly interval of approximately 8 hours, may replace the long established 24 hour collection for diagnosis and follow-up in patients with SI-NETs.