Program in International and Community Nutrition, Department of Nutrition, University of California, Davis, CA.
Nutrition and Global Development, Bill & Melinda Gates Foundation, Seattle, WA.
Am J Clin Nutr. 2019 May 1;109(5):1484-1492. doi: 10.1093/ajcn/nqz014.
Cross-sectional (CS) surveys indicate that individuals with acute inflammation have higher plasma ferritin (pF), and lower retinol-binding protein (RBP) and zinc (pZn) concentrations than those without. In populations with a high burden of infection, correction factors (CFs) or regression corrections (RCs) are applied to biomarkers to estimate the prevalence of micronutrient (MN) deficiencies adjusted for inflammation. This assumes that individuals with and without inflammation have the same nutritional status, which may not be the case.
The aim of this study was to investigate relations between short-term, longitudinal within-individual changes in acute phase proteins (C-reactive protein [CRP], α-1-acid glycoprotein [AGP]) and biomarkers of MN status (pF, soluble transferrin receptor [sTfR], RBP, and pZn), and compare them to CS differences.
Two blood samples were obtained 21 d apart from 451 asymptomatic Burkinabé children aged 6-23 mo. To calculate CFs, inflammation was defined as CRP >5 mg/L or AGP >1 g/L, or both. The RC approach adjusted MN biomarkers to a presumably healthy reference point within the study population (10th percentile CRP or AGP concentration). CS CFs and RCs were estimated from a naive regression model, treating observations from the same children as independent. Longitudinal CFs and RCs, to estimate effects of within-individual changes in CRP and/or AGP, were estimated from general linear models, accounting for repeated measures.
In CS models, geometric mean pF and sTfR concentrations were 8-340% greater, and RBP and pZn 2-18% lower, in children with inflammation than those without. Except for sTfR, biomarker concentrations differed in the same direction and by similar magnitude within individuals whose inflammation status changed during the observation period. Although geometric mean MN concentrations differed significantly when adjusted with CS compared with longitudinal models, the estimated prevalence of MN deficiencies in CS and longitudinally adjusted models was similar.
The CF and RC approaches to adjust MN biomarkers for inflammation between individuals in CS surveys are valid approaches for data collection and programmatic decisions in comparable populations. This study was registered at clinicaltrials.gov as NCT00944853.
横断面（CS）调查表明，急性炎症患者的血浆铁蛋白（pF）较高，视黄醇结合蛋白（RBP）和锌（pZn）浓度较低，而非炎症患者。在感染负担高的人群中，应用校正因子（CFs）或回归校正（RCs）对生物标志物进行校正，以估计炎症调整后的微量营养素（MN）缺乏症的患病率。这假设炎症患者和非炎症患者具有相同的营养状况，但事实可能并非如此。
本研究旨在调查急性期蛋白（C 反应蛋白[CRP]、α-1 酸性糖蛋白[AGP]）与 MN 状态的生物标志物（pF、可溶性转铁蛋白受体[sTfR]、RBP 和 pZn）的短期、纵向个体内变化之间的关系，并将其与 CS 差异进行比较。
从 451 名无症状布基纳法索儿童中采集相隔 21 天的两份血样，年龄为 6-23 个月。为了计算 CFs，将 CRP>5mg/L 或 AGP>1g/L 或两者均定义为炎症。RC 方法将 MN 生物标志物调整到研究人群中假定的健康参考点（CRP 或 AGP 浓度的第 10 百分位数）。CS CFs 和 RCs 是从简单回归模型中估计的，将来自同一儿童的观察值视为独立的。从一般线性模型中估计估计个体内 CRP 和/或 AGP 变化的纵向 CFs 和 RCs，考虑到重复测量。
在 CS 模型中，与无炎症的儿童相比，炎症儿童的 pF 和 sTfR 浓度的几何平均值高 8-340%，RBP 和 pZn 浓度低 2-18%。除了 sTfR 之外，在观察期间炎症状态发生变化的个体中，生物标志物浓度以相同的方向和相似的幅度发生变化。尽管与纵向模型相比，CS 模型中调整后的 MN 浓度差异有统计学意义，但 CS 和纵向调整模型中 MN 缺乏症的估计患病率相似。
CS 调查中个体间调整 MN 生物标志物炎症的 CF 和 RC 方法是在可比人群中进行数据收集和计划决策的有效方法。本研究在 clinicaltrials.gov 注册为 NCT00944853。
