National Institute of Public Health and the Environment, Bilthoven, the Netherlands.
Nutr Cancer. 2013;65(1):17-24. doi: 10.1080/01635581.2013.741754.
Many epidemiological studies assess nutritional status based on single blood measurements, without verifying if these remain reliable over repeated measurements. This study assessed the reliability over a period of 2 to 5 yr of plasma carotenoids, vitamin C, retinol, tocopherols, and serum compounds involved in 1-carbon metabolism in a subsample of Dutch participants of European Prospective Investigation into Cancer and Nutrition (EPIC). Blood samples from 38 men from MORGEN-EPIC and 35 women from Prospect-EPIC were collected between 1993 and 1997 and again after 2 to 5 yr. The reliability of plasma carotenoids, retinol, vitamin C, and tocopherols, and of serum folate, homocysteine, and vitamins B6 and B12 was estimated using an intraclass correlation coefficient (ICC). Serum homocysteine and vitamin B12 were highly reliable biomarkers, with ICCs of 0.91 and 0.75, respectively. All other analyzed biomarkers had a slight or fair reliability over several years (ICCs ranged from 0.17 to 0.56). Most examined biomarkers showed reliability values that may lead to considerable attenuation of the risk estimate when used as exposure assessment in a risk model. If multiple measurements are not available, the risk estimates can be adjusted for the regression dilution using the ICC as adjustment coefficient.
许多流行病学研究基于单次血液测量来评估营养状况，而没有验证这些测量在多次测量中是否仍然可靠。本研究评估了荷兰欧洲癌症前瞻性调查和营养研究（EPIC）的一个亚组参与者的血浆类胡萝卜素、维生素 C、视黄醇、生育酚和参与 1 碳代谢的血清化合物在 2 至 5 年内的可靠性。MORGEN-EPIC 的 38 名男性和 Prospect-EPIC 的 35 名女性的血液样本分别于 1993 年至 1997 年以及 2 至 5 年后采集。使用组内相关系数（ICC）估计了血浆类胡萝卜素、视黄醇、维生素 C 和生育酚以及血清叶酸、同型半胱氨酸、维生素 B6 和 B12 的可靠性。血清同型半胱氨酸和维生素 B12 是高度可靠的生物标志物，ICC 分别为 0.91 和 0.75。其他分析的生物标志物在几年内具有轻微或适度的可靠性（ICC 范围为 0.17 至 0.56）。大多数检查的生物标志物显示出可靠性值，如果在风险模型中用作暴露评估，可能会导致风险估计值大大降低。如果无法获得多次测量，则可以使用 ICC 作为调整系数，通过回归稀释来调整风险估计值。
