Endocrine Abstracts

Introduction: In patients with neuroendocrine tumours (NETs), the urinary concentration of the serotonin metabolite 5-hydroxyindole acetic acid (5-HIAA) is used to monitor disease progression or response to treatment. The sensitivity and specificity in the presence of the carcinoid syndrome are approximately 70 and 90%, respectively. However, there are problems with the accurate meaurement of a 24-h collection, and this is often inconvenient for patients. In addition, serotonin-containing foods may increase urinary 5-HIAA levels and require food avoidance. The aim of this study was to assess the correlation between 5-HIAA concentration in a spot-urine sample with the 24h-urine collection.

Methods: Consecutive patients with NETs or symptoms suggestive of NETs seen in our Endocrine-Oncology Clinic provided a 24h-urine collection and a spot-urine for 5-HIAA assessment. Written advice to avoid serotonin-rich food for three days prior to collection was given. Urine 5-HIAA was analysed by high-performance liquid chromatography (HPLC). As previously suggested by the group at King’s Hospital London, a cut-off value of 5 mol/mmol for spot urinary 5-HIAA was used as the upper reference limit.

Results: We included 102 paired samples from 85 patients: 49/85 (58%) were male, the mean age was 64.7 (S.D. 14.1) years, and 76/85 (89%) had a previous NET diagnosis. Based on the 24h-urine collection, 58 measurements were above the reference value (5-HIAA >40 μmol/24 h) and 52 from spot specimens were above the upper limit of 5 mol/mmol. A spot-urine was concordant with 24h-urine results in 88.2%. The Spearman correlation between 5-HIAA measured in the 24h-urine and the spot-urine was +0.88. Using the 24h-urine collection as a gold standard, the spot-urine had a sensitivity of 84.5% and a specificity of 93.1%.

Conclusions: These results suggest that spot-urine is a simple and promising sample type for 5-HIAA analysis, in particular for follow-up in patients with known elevated 5-HIAA levels.