Comparison of Serum and Urinary 5-Hydroxyindoleacetic Acid as Biomarker for Neuroendocrine Neoplasms

Abstract

Context: Patients with serotonin-secreting neuroendocrine neoplasms (NENs) have increased serum 5-hydroxyindoleacetic acid (5HIAA) concentrations. Serum 5HIAA thus serves as a biomarker in NEN. Objective: To evaluate an improved tandem mass spectrometric serum 5HIAA assay for diagnosis and follow-up of NEN in a clinical cohort. Design: A retrospective study during 2016-2018 at the Diagnostic Center and Department of Endocrinology at Helsinki University Hospital, Finland. Methods: Detailed patient data was obtained from 116 patients. Serum 5HIAA was analyzed by 2 different liquid chromatography with tandem mass spectrometry (LC-MS/MS) assays with samples prepared either by protein precipitation or solid phase extraction. Twenty-four-hour urine 5HIAA samples (n = 33) were analyzed by amperometric LC, and the results were compared. Specificity and sensitivity were calculated by receiver operating characteristic (ROC) analysis. Results: We achieved 5 to 10 000 nmol/L linearity and Conclusion: Serum 5HIAA by LC-MS/MS after protein precipitation performs equally well for the diagnosis of NEN as urinary 5HIAA LC assay. The outcome and sensitivity for serum and 24-h urine assays are convergent. Due to much more reliable and convenient sampling, we recommend serum instead of 24-h urine 5HIAA for diagnosis and follow-up of NEN patients.