Department of Clinical Biochemistry, Hvidovre Hospital, University of Copenhagen, Denmark.
Clin Chem Lab Med. 2011 Feb;49(2):291-5. doi: 10.1515/CCLM.2011.054. Epub 2010 Nov 23.
Trisomy 21 risk estimation in first trimester pregnancies can be performed by a combined test based on ultrasound measurement of fetal nuchal translucency thickness and maternal plasma concentrations of free β human chorionic gonadotropin (hCGβ) and pregnancy-associated plasma protein A (PAPP-A). However, little knowledge exists regarding the biological variation of hCGβ and PAPP-A when the time interval between sampling increases.
We estimated these variations from double measurements of hCGβ and PAPP-A in first trimester pregnancies in 167 women. Data were divided into three groups based on the number of days between sampling. The correlation coefficients and biological variation were estimated for each group.
The correlation coefficient between the first and second samples was 0.841 for hCGβ, and 0.706 for PAPP-A. The ranges for biological variation were 11.9%-48.5% for hCGβ and 31.6%-63.3% for PAPP-A, increasing with time between sampling. The average overall biological variation for hCGβ was 29%, and 49.7% for PAPP-A.
We found high biological variation for plasma concentrations of hCGβ and PAPP-A, increasing with longer time intervals between sampling. From our data that showed high correlation of hCGβ and PAPP-A in the first and second sample, we found no reason to recommend retesting. However, new studies should clarify whether PAPP-A should be collected early, and hCGβ late, in the first trimester of pregnancy.
唐氏综合征（21 三体）风险可通过基于胎儿颈项透明层厚度（nuchal translucency thickness，NT）联合母体游离人绒毛膜促性腺激素（β-human chorionic gonadotropin，β-hCG）和妊娠相关血浆蛋白 A（pregnancy-associated plasma protein A，PAPP-A）浓度的联合检测进行评估。然而，当两次采血间隔时间延长时，hCGβ 和 PAPP-A 的生物学变异情况却知之甚少。
我们对 167 例早孕期孕妇进行了 hCGβ 和 PAPP-A 的重复检测，以评估其生物学变异。根据两次采血的间隔天数，将数据分为三组。为每组数据计算了相关系数和生物学变异。
hCGβ 与 PAPP-A 两次检测的相关系数分别为 0.841 和 0.706。hCGβ 和 PAPP-A 的生物学变异范围分别为 11.9%-48.5%和 31.6%-63.3%，且随两次采血间隔时间的延长而增加。hCGβ 的平均总生物学变异为 29%，PAPP-A 的为 49.7%。
我们发现 hCGβ 和 PAPP-A 的血浆浓度具有较高的生物学变异，且随两次采血间隔时间的延长而增加。根据我们的研究数据，hCGβ 和 PAPP-A 两次检测间具有高度相关性，因此我们不建议重复检测。然而，仍需要进一步的研究来明确 PAPP-A 是否应在早孕期早期采集，而 hCGβ 则应在晚孕期采集。
