Department of Chemical Pathology, National Health Laboratory Service and University of the Witwatersrand, Johannesburg, South Africa.
Clin Chem Lab Med. 2023 Jul 7;61(12):2150-2158. doi: 10.1515/cclm-2023-0339. Print 2023 Nov 27.
C-peptide and insulin are peptide hormones and their stability is affected by a number of pre-analytical factors. The study aimed to investigate the impact of sample type, storage temperature and time delays before centrifugation and analysis on the stability of C-peptide and insulin.
Ten healthy non-diabetic adults in fasting and non-fasting state were enrolled. 40 mL of blood was collected from each participant into SST and dipotassium EDTA tubes. Samples were centrifuged immediately or at timed intervals (8, 12, 48 and 72 h). After baseline measurements on the Roche Cobas e602 analyzer using electrochemiluminescence immunoassays, aliquots were stored at room temperature (RT), 2-8 and -20 °C for 4 h to 30 days. The percentage deviation (PD) from baseline was calculated and a change greater than desirable biological variation total error was considered clinically significant.
C-peptide was more stable in separated serum than plasma (PD of -5 vs. -13 %) samples stored at 2-8 °C for 7 days and was most unstable at RT when centrifugation was delayed (PD -46 % in plasma and -74 % in serum after 48 h). Insulin was more stable in plasma than in serum under the different storage conditions with a minimum PD of -1% when stored at -20 °C for 30 days. When samples were kept unspun at RT for 72 h, PD was -23 and -80 % in plasma and serum, respectively.
C-peptide was more stable in serum provided the sample was centrifuged immediately and stored in the fridge or freezer while insulin was found to be more stable in EDTA plasma.
C 肽和胰岛素是肽类激素，其稳定性受到许多分析前因素的影响。本研究旨在探讨样本类型、储存温度以及离心和分析前的时间延迟对 C 肽和胰岛素稳定性的影响。
纳入 10 名空腹和非空腹的健康非糖尿病成年人。每位参与者采集 40ml 血液，分别注入 SST 和二钾 EDTA 管中。立即离心或在不同时间点（8、12、48 和 72 小时）离心。使用电化学发光免疫分析法在罗氏 Cobas e602 分析仪上进行基线测量后，将等分试样储存于室温（RT）、2-8°C 和-20°C 下 4 小时至 30 天。计算与基线的百分比偏差（PD），且将大于理想生物学变异总误差的变化视为临床显著。
与储存于 2-8°C 7 天的血浆（PD-13%）相比，分离血清中 C 肽更为稳定（PD-5%），而当延迟离心时，在 RT 下最不稳定（血浆中 PD-46%，血清中 PD-74%，48 小时后）。在不同储存条件下，胰岛素在血浆中比血清中更稳定，在-20°C 储存 30 天时 PD 最小为-1%。当样本在 RT 下未离心且储存 72 小时时，在血浆和血清中 PD 分别为-23%和-80%。
在立即离心并冷藏或冷冻储存的情况下，血清中 C 肽更为稳定，而胰岛素在 EDTA 血浆中更稳定。
