Endocrine Abstracts

Introduction: Neuroendocrine tumours (NET) are a diverse group of neoplasms originating from cells within the diffuse endocrine system. Urine 5-HIAA is commonly used in the diagnosis and monitoring of patients with NET in particular small intestinal neuroendocrine tumour with carcinoid syndrome. Urine 5-HIAA collection over a 24 hour period and the potential exposure to acid preservative in the sample container, limit the use of urine 5-HIAA.

Methods: Samples were obtained from 80 patients with NET and 30 healthy volunteers. We developed and validated a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for plasma and serum 5-HIAA. Sensitivities and specificities of the plasma and serum 5-HIAA assays were assessed using a ROC curve. Comparison was made between urine 5-HIAA and 5-HIAA in plasma and serum.

Results: The assay showed acceptable analytical performance. Area under the curve (AUC) from ROC analysis for plasma 5-HAA was 0.899 and 0.902 for serum 5-HIAA. Sensitivity of 91.2% with a specificity of 61.9% were obtained at a cut off of 135 nmol/l for both plasma and serum 5-HIAA. A statistically significant correlation was observed between the plasma and serum 5-HIAA assay. Bland-Altman analysis showed a good agreement between both assays. A statistically significant agreement was shown when plasma and serum 5-HIAA was compared with urine 5-HIAA in patients with NET, κ = 0.675 (95% CI 0.49 to 0.86), P < 0.001. Similar finding was observed in healthy volunteers when plasma and serum 5-HIAA was compared with urine 5-HIAA, 0.967 (95% CI 0.828 to 0.999), P=<0.001.

Conclusion: We developed an LC-MS/MS assay for plasma and serum 5-HIAA and have demonstrated that they compare well with the urine 5-HIAA assay. The plasma and serum 5-HIAA assays were shown to be comparable; hence either sample type may be used as an alternative to the urine 5-HIAA assay.