Department of Chemical and Biological Sciences, Universidad de Sonora, Hermosillo, Sonora, Mexico.
Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA.
J Nutr. 2021 Dec 3;151(12):3874-3881. doi: 10.1093/jn/nxab310.
Vitamin A status may influence the choice of a blood sampling time for applying the retinol isotope dilution (RID) equation to predict vitamin A total body stores (TBS) in children.
We aimed to identify time(s) after administration of labeled vitamin A that provide accurate estimates of TBS in theoretical children with low or high TBS.
We postulated 2- to 5-y-old children (12/group) with low (<200 μmol) or high TBS (≥700 μmol) and used compartmental analysis to simulate individual subject values for the RID equation TBS = FaS/SAp (Fa, fraction of dose in stores; S, retinol specific activity in plasma/in stores; SAp, retinol specific activity in plasma). Using individual SAp and group geometric mean FaS values from 1-28 d, we calculated individual and group mean TBS and compared them to assigned values.
Mean TBS was accurately predicted for both groups at all times. For individuals, predicted and assigned TBS were closest when the CV% for FaS was low [12-14%; 4-13 d (low), 12-28 d (high)]. The mean percentage error for TBS was <10% from 2-19 d (low) and 7-28 d (high). Predicted TBS was within 25% of assigned TBS for ≥80% of children from 3-23 d (low) and 9-28 d (high). Within groups, RID tended to overestimate lower TBS and underestimate higher TBS.
Using a good estimate for FaS, accurate RID predictions of TBS for individuals will be obtained at many times. If vitamin A status is low, results indicate that early sampling (e.g., 4-13 d) is optimal; if vitamin A status is high, sampling at 12-28 d is indicated. When vitamin A status is unknown, sampling at 14 d is recommended, or a super-subject design can be used to obtain the group mean FaS at various times for RID prediction of TBS in individuals.
维生素 A 状态可能会影响应用视黄醇同位素稀释 (RID) 方程来预测儿童维生素 A 总体储存量 (TBS) 的采血时间选择。
我们旨在确定在理论上低或高 TBS 的儿童中，给予标记的维生素 A 后何时能提供 TBS 的准确估计值。
我们假设 2-5 岁的儿童（每组 12 人）TBS 低（<200 μmol）或高（≥700 μmol），并使用房室分析来模拟 RID 方程 TBS = FaS/SAp（Fa，剂量在储存中的分数；S，血浆/储存中视黄醇的比活度；SAp，血浆中视黄醇的比活度）中个体的个体值。使用 1-28 天的个体 SAp 和组几何平均 FaS 值，我们计算了个体和组平均 TBS，并将其与分配值进行了比较。
两组在所有时间的 TBS 均得到了准确的预测。对于个体而言，当 FaS 的 CV% 较低时（12-14%；4-13d（低），12-28d（高）），预测和分配的 TBS 最接近。TBS 的平均百分比误差<10%，从 2-19d（低）和 7-28d（高）。从 3-23d（低）和 9-28d（高），预测 TBS 在 80%以上的儿童中均在 25%以内接近分配的 TBS。在组内，RID 倾向于高估较低的 TBS 并低估较高的 TBS。
使用 FaS 的良好估计值，将在许多时间获得个体 TBS 的准确 RID 预测。如果维生素 A 状态较低，则表明早期采样（例如 4-13d）最佳；如果维生素 A 状态较高，则建议在 12-28d 时采样。当维生素 A 状态未知时，建议在 14d 时采样，或者可以使用超级个体设计在不同时间获得组平均 FaS，以便 RID 预测个体的 TBS。
