Clin Chem Lab Med. 2013 Sep;51(9):1781-8. doi: 10.1515/cclm-2012-0805.
Theoretically, repeated sampling of free β-human chorionic gonadotropin (hCGβ) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester of pregnancy might improve performance of risk assessment of trisomy 21 (T21). To assess the performance of a screening test involving repeated measures of biochemical markers, correlations between markers must be estimated. The aims of this study were to calculate the autocorrelation and cross-correlation between hCGβ and PAPP-A in the first trimester of pregnancy and to investigate the possible impact of gestational age at the first sample and time between sampling on the correlation.
A prospective study was conducted including 3891 unaffected singleton pregnancies. Two measurements of hCGβ and PAPP-A were obtained during the first trimester in each pregnancy. Correlations between the four parameters, hCGβ first, hCGβ second, PAPP-A first and PAPP-A second, were estimated and presented in terms of Pearson's r coefficients. Furthermore, the correlation between paired samples as a function of time between samples was investigated.
The study demonstrated high correlation between first and second samples of hCGβ and PAPP-A with a correlation coefficient of 0.80 and 0.79, respectively. By contrast, the correlations between hCGβ and PAPP-A were low. In addition, the study demonstrated that the correlation between paired samples of hCGβ and PAPP-A decreases with earlier gestational age at the first sample and with increasing time between samples.
We have developed a parameter set in terms of correlations between biochemical markers, which can be incorporated into a T21 screening algorithm based on repeated measures within the first trimester.
理论上，在妊娠早期重复采集游离β-人绒毛膜促性腺激素（hCGβ）和妊娠相关血浆蛋白-A（PAPP-A）样本，可能会提高 21 三体（T21）风险评估的性能。为了评估涉及生化标志物重复测量的筛查试验的性能，必须估计标志物之间的相关性。本研究的目的是计算妊娠早期 hCGβ 和 PAPP-A 之间的自相关和互相关，并探讨第一个样本的孕龄和两次采样之间的时间间隔对相关性的可能影响。
进行了一项前瞻性研究，纳入了 3891 例无异常的单胎妊娠。在每个妊娠的妊娠早期，分别进行了两次 hCGβ 和 PAPP-A 的测量。估计了四个参数（hCGβ 第一次、hCGβ 第二次、PAPP-A 第一次和 PAPP-A 第二次）之间的相关性，并以 Pearson r 系数表示。此外，还研究了随着两次采样之间时间的变化，配对样本之间的相关性。
研究表明，hCGβ 和 PAPP-A 的第一次和第二次样本之间具有高度相关性，相关系数分别为 0.80 和 0.79。相比之下，hCGβ 和 PAPP-A 之间的相关性较低。此外，研究表明，hCGβ 和 PAPP-A 配对样本之间的相关性随着第一个样本的孕龄较早和两次采样之间的时间间隔增加而降低。
我们已经开发了一套基于生化标志物之间相关性的参数集，可将其纳入基于妊娠早期重复测量的 T21 筛查算法中。
