Serotonin (5-hydroxytryptamine, 5-HT) is readily secreted in patients with carcinoid tumors, especially arising from the midgut. Although serotonin assay in human plasma or whole blood has been extensively studied, serotonin assay in human serum by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has received much less attention. In this study, a simple and reliable LC-MS/MS method based on one step protein precipitation for sample pretreatment was developed for clinical assay of serum serotonin. Namely, 150 μL of serum was mixed with 50 μL of internal standard (IS) and 200 μL of 4 wt.% 5-sulfosalicylic acid (SSA) solution for protein precipitation. The supernatant after centrifugation was analyzed directly without further treatment. This method was validated for consistent linearity from 0.94-240 ng/mL with CVs≤11.7%, good recovery in the range of 87.5-104%, excellent analyte stability and low carryover. No obvious matrix effect was observed. Intra- and inter-day imprecision were below 8.03% and 11.5% respectively. Dilution linearity was verified with satisfying linearly dependent coefficients (r²= 0.9937). The reference interval of serotonin was established from 126 results derived from subjects without carcinoid tumors. Therefore, apart from development of a serum serotonin assay by the LC-MS/MS method, the reference interval (RI) of 5-HT has also been established for clinical testing in patients with carcinoid diseases. In addition, this method has been successfully used in our laboratory, indicating that this robust LC-MS/MS assay with simple sample preparation and short analysis time could offer inspiring potential for clinical testing of 5-HT in routine clinical laboratories.

5-羟色胺（5-羟色胺，5-HT）容易在类癌患者中分泌，尤其是中肠引起的患者。尽管已经广泛研究了人血浆或全血中的血清素测定，但是通过液相色谱-串联质谱法（LC-MS / MS）在人血清中的血清素测定受到的关注较少。在这项研究中，开发了一种基于一步蛋白质沉淀的简单可靠的LC-MS / MS方法进行样品预处理，用于血清5-羟色胺的临床测定。即，将150μL血清与50μL内标（IS）和200μL4 wt％的5-磺基水杨酸（SSA）溶液混合以进行蛋白质沉淀。无需进一步处理即可直接分析离心后的上清液。验证了该方法在0.94-240 ng / mL范围内的恒定线性，且CVs≤11.7％，在87.5-104％的范围内具有良好的回收率，出色的分析物稳定性和低残留。没有观察到明显的基质效应。日内和日间不精确度分别低于8.03％和11.5％。通过满足线​​性相关系数（r² = 0.9937）。血清素的参考间隔是根据无类癌肿瘤受试者的126个结果确定的。因此，除了通过LC-MS / MS方法开发血清5-羟色胺测定法外，还建立了5-HT参考区间（RI）用于类癌疾病患者的临床检测。此外，该方法已在我们的实验室中成功使用，表明这种鲁棒的LC-MS / MS测定方法具有简单的样品制备和较短的分析时间，可为常规临床实验室中的5-HT临床测试提供启发性的潜力。